Remove a support of ISA addresses predefined at compile time. It is
unused (filled by zeroes) and prolongs the code. Don't initialize global
array and add `ioaddr' module param description.
Signed-off-by: Jiri Slaby <jirislaby@gmail.com>
Acked-by: Alan Cox <alan@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
- use dev_* for printing in pci probe function
- move ISA p[rints directly into isa find function, do not postpone it.
Remove macros bound to it then.
- prepend some prints by "mxser: " to know what it belongs to
Signed-off-by: Jiri Slaby <jirislaby@gmail.com>
Acked-by: Alan Cox <alan@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
- remove unused mxvar_diagflag
- move mxser_msr into the only user/function
- GMStatus, hmm, fix race-prone access to it. We need only one instance for
real, not MXSER_PORTS. Move it to MOXA_GETMSTATUS ioctl.
- mxser_mon_ext, almost the same, but alloc it on heap, since it has more than
2 kilos.
- fix indexing, `i' is not the index value, `i * MXSER_PORTS_PER_BOARD + j' is
Signed-off-by: Jiri Slaby <jirislaby@gmail.com>
Acked-by: Alan Cox <alan@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
- remove break ctl from ioctl handler, it's never reached, since
tty_ops->break_ctl is defined (mxser break handling is done in software)
- mark MOXA_GET_MAJOR as deprecated
- fix TIOCGICOUNT (some retval non-checks of put_user). Use copy_to_user
to whole structure instead.
Signed-off-by: Jiri Slaby <jirislaby@gmail.com>
Acked-by: Alan Cox <alan@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Tim Schmielau <tim@physik3.uni-rostock.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Push the BKL down into the driver ioctl methods
Signed-off-by: Alan Cox <alan@redhat.com>
Cc: Jiri Slaby <jirislaby@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Also fix the capability checking for firmware load.
Signed-off-by: Alan Cox <alan@redhat.com>
Cc: Jiri Slaby <jirislaby@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Push the BKL down to the point it wraps the actual mwave method handlers
Signed-off-by: Alan Cox <alan@redhat.com>
Cc: Eric Sesterhenn <snakebyte@gmx.de>
Cc: Yani Ioannou <yani.ioannou@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
(The tty side is already done)
Signed-off-by: Alan Cox <alan@redhat.com>
Cc: Jiri Slaby <jirislaby@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Push it down as far as the EFI method calls. Someone who knows EFI can do
the other bits. Also fix another wrong unknown ioctl return.
Signed-off-by: Alan Cox <alan@redhat.com>
Cc: Joe Perches <joe@perches.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This patch #if 0's the unused hpet_unregister().
Signed-off-by: Adrian Bunk <bunk@kernel.org>
Acked-by: Clemens Ladisch <clemens@ladisch.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This patch adds a proper extern for mwave_s_mdd in
drivers/char/mwave/mwavedd.h
Signed-off-by: Adrian Bunk <bunk@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This adds a driver supporting a family of I2C port expanders from Maxim,
which includes the MAX7319 and MAX7320-7327 chips.
[dbrownell@users.sourceforge.net: minor fixes]
Signed-off-by: Jack Ren <jack.ren@marvell.com>
Signed-off-by: Eric Miao <eric.miao@marvell.com>
Acked-by: Jean Delvare <khali@linux-fr.org>
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This patch adds functionality to the gpio-lib subsystem to make it
possible to enable the gpio-lib code even if the architecture code didn't
request to get it built in.
The archtitecture code does still need to implement the gpiolib accessor
functions in its asm/gpio.h file. This patch adds the implementations for
x86 and PPC.
With these changes it is possible to run generic GPIO expansion cards on
every architecture that implements the trivial wrapper functions. Support
for more architectures can easily be added.
Signed-off-by: Michael Buesch <mb@bu3sch.de>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: David Brownell <david-b@pacbell.net>
Cc: Russell King <rmk@arm.linux.org.uk>
Cc: Haavard Skinnemoen <hskinnemoen@atmel.com>
Cc: Jesper Nilsson <jesper.nilsson@axis.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Jean Delvare <khali@linux-fr.org>
Cc: Samuel Ortiz <sameo@openedhand.com>
Cc: Kumar Gala <galak@gate.crashing.org>
Cc: Sam Ravnborg <sam@ravnborg.org>
Cc: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This adds the bt8xxgpio driver. The purpose of the bt8xxgpio driver is to
export all of the 24 GPIO pins available on Brooktree 8xx chips to the
kernel GPIO infrastructure.
This makes it possible to use a physically modified BT8xx card as
cheap digital GPIO card.
[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Michael Buesch <mb@bu3sch.de>
Cc: David Brownell <david-b@pacbell.net>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Mauro Carvalho Chehab <mchehab@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Teach the mcp23s08 driver about a curious feature of these chips: up to
four of them can share the same chipselect, with the SPI signals wired in
parallel, by matching two bits in the first protocol byte against two
address lines on the chip.
This is handled by three software changes:
* Platform data now holds an array of per-chip structs, not
just one chip's address and pullup configuration.
* Probe() and remove() now use another level of structure,
wrapping an instance of the original structure for each
mcp23s08 chip sharing that chipselect.
* The HAEN bit is set, so that the hardware address bits can no
longer be ignored (boot firmware may not have enabled them).
The "one struct per chip" preserves the guts of the current code,
but platform_data will need minor changes.
OLD:
/* incorrect "slave" ID may not have mattered */
.slave = 3,
.pullups = BIT(3) | BIT(1) | BIT(0),
NEW:
/* slave address _must_ match chip's wiring */
.chip[3] = {
.is_present = true,
.pullups = BIT(3) | BIT(1) | BIT(0),
},
There's no change in how things _behave_ for spi_device nodes with a
single mcp23s08 chip. New multi-chip configurations assign GPIOs in
sequence, without holes. The spi_device just resembles a bigger
controller, but internally it has multiple gpio_chip instances.
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This adds a simple sysfs interface for GPIOs.
/sys/class/gpio
/export ... asks the kernel to export a GPIO to userspace
/unexport ... to return a GPIO to the kernel
/gpioN ... for each exported GPIO #N
/value ... always readable, writes fail for input GPIOs
/direction ... r/w as: in, out (default low); write high, low
/gpiochipN ... for each gpiochip; #N is its first GPIO
/base ... (r/o) same as N
/label ... (r/o) descriptive, not necessarily unique
/ngpio ... (r/o) number of GPIOs; numbered N .. N+(ngpio - 1)
GPIOs claimed by kernel code may be exported by its owner using a new
gpio_export() call, which should be most useful for driver debugging.
Such exports may optionally be done without a "direction" attribute.
Userspace may ask to take over a GPIO by writing to a sysfs control file,
helping to cope with incomplete board support or other "one-off"
requirements that don't merit full kernel support:
echo 23 > /sys/class/gpio/export
... will gpio_request(23, "sysfs") and gpio_export(23);
use /sys/class/gpio/gpio-23/direction to (re)configure it,
when that GPIO can be used as both input and output.
echo 23 > /sys/class/gpio/unexport
... will gpio_free(23), when it was exported as above
The extra D-space footprint is a few hundred bytes, except for the sysfs
resources associated with each exported GPIO. The additional I-space
footprint is about two thirds of the current size of gpiolib (!). Since
no /dev node creation is involved, no "udev" support is needed.
Related changes:
* This adds a device pointer to "struct gpio_chip". When GPIO
providers initialize that, sysfs gpio class devices become children of
that device instead of being "virtual" devices.
* The (few) gpio_chip providers which have such a device node have
been updated.
* Some gpio_chip drivers also needed to update their module "owner"
field ... for which missing kerneldoc was added.
* Some gpio_chips don't support input GPIOs. Those GPIOs are now
flagged appropriately when the chip is registered.
Based on previous patches, and discussion both on and off LKML.
A Documentation/ABI/testing/sysfs-gpio update is ready to submit once this
merges to mainline.
[akpm@linux-foundation.org: a few maintenance build fixes]
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Cc: Guennadi Liakhovetski <g.liakhovetski@pengutronix.de>
Cc: Greg KH <greg@kroah.com>
Cc: Kay Sievers <kay.sievers@vrfy.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The sm501_gpio_pin2nr() routine returns the wrong values for gpios in the
upper bank.
Signed-off-by: Ben Dooks <ben-linux@fluff.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Fix the build problems if CONFIG_MFD_SM501_GPIO is not set, which is
generally when there is no gpiolib support available as currently happens
on x86 when building PCI SM501.
Signed-off-by: Ben Dooks <ben-linux@fluff.org>
Tested-by: Li Zefan <lizf@cn.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Fixup the comments from the patch that added the gpiolib support from
Andrew Morton. These include spotting some missing frees on error or
release, and changing a memcpy for a type-safe assingment.
Signed-off-by: Ben Dooks <ben-linux@fluff.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Add support for adding the GPIO based I2C resources.
Signed-off-by: Ben Dooks <ben-linux@fluff.org>
Cc: Arnaud Patard <apatard@mandriva.com>
Cc: David Brownell <david-b@pacbell.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The SM501 PCI card requires a dyanmic gpio allocation as the number of
cards is not known at compile time. Fixup the platform data and
registration to deal with this.
Acked-by: Ben Dooks <ben-linux@fluff.org>
Signed-off-by: Arnaud Patard <apatard@mandriva.com>
Cc: David Brownell <david-b@pacbell.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Add support for exporting the GPIOs on the SM501 via gpiolib.
Signed-off-by: Ben Dooks <ben-linux@fluff.org>
Cc: Arnaud Patard <apatard@mandriva.com>
Cc: David Brownell <david-b@pacbell.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Add callback to get or set the power control if the device has the sleep
connected to some form of GPIO.
Signed-off-by: Ben Dooks <ben-linux@fluff.org>
Cc: Arnaud Patard <apatard@mandriva.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
We want to use WARN() as a variant of WARN_ON(), however a few drivers are
using WARN() internally. This patch renames these to WARNING() to avoid the
namespace clash. A few cases were defining but not using the thing, for those
cases I just deleted the definition.
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Acked-by: Greg KH <greg@kroah.com>
Cc: Karsten Keil <kkeil@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
m68k allmodconfig:
drivers/misc/hpilo.c: In function 'ilo_ccb_close':
drivers/misc/hpilo.c:225: error: implicit declaration of function 'pci_free_consistent'
drivers/misc/hpilo.c: In function 'ilo_ccb_open':
drivers/misc/hpilo.c:244: error: implicit declaration of function 'pci_alloc_consistent'
drivers/misc/hpilo.c:245: warning: assignment makes pointer from integer without a cast
Cc: David Altobelli <david.altobelli@hp.com>
Cc: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Since 43cc71eed1 (platform: prefix MODALIAS
with "platform:"), the platform modalias is prefixed with "platform:".
Add MODULE_ALIAS() to the hotpluggable parport platform drivers, to
re-enable auto loading.
Signed-off-by: Kay Sievers <kay.sievers@vrfy.org>
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Cc: Greg KH <greg@kroah.com>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
Acked-by: Ben Dooks <ben-linux@fluff.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Since 43cc71eed1 (platform: prefix MODALIAS
with "platform:"), the platform modalias is prefixed with "platform:".
Add MODULE_ALIAS() to the MFD platform drivers, to re-enable auto loading.
[dbrownell@users.sourceforge.net: one was missing]
Signed-off-by: Kay Sievers <kay.sievers@vrfy.org>
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Cc: Greg KH <greg@kroah.com>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
Cc: Samuel Ortiz <samuel@sortiz.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Since 43cc71eed1 ("platform: prefix MODALIAS
with "platform:"), the platform modalias is prefixed with "platform:".
Add MODULE_ALIAS() to the hotpluggable "power" drivers drivers, to
re-enable auto loading.
[dbrownell@users.sourceforge.net: one was missing]
Signed-off-by: Kay Sievers <kay.sievers@vrfy.org>
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Cc: Greg KH <greg@kroah.com>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This driver adds support for reading and configuring certain information
on modern HP laptops with WMI BIOS interfaces. It supports enabling and
disabling the ambient light sensor, querying attached displays and hard
drive temperature, sending events on docking and querying the state of the
dock and toggling the state of the wifi, bluetooth and wwan hardware via
rfkill. It also makes the little "(i)" button work on machines that send
that via WMI rather than via the keyboard controller.
Signed-off-by: Matthew Garrett <mjg@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Some bits were missed when the tipar driver was removed.
Signed-off-by: Adrian Bunk <bunk@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
For it doesn't exist on i386.
Cc: Ian Molton <spyro@f2s.com>
Cc: Dmitry Baryshkov <dbaryshkov@gmail.com>
Cc: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Both commits 0f17e4c796 ("Add missing
semaphore.h includes") and 4933d07531
("m68k: drivers/input/serio/hp_sdc.c needs <linux/semaphore.h>") added a
We only really need one ;)
Reported-by: Huang Weiyi <weiyi.huang@gmail.com>
Requested-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
To prepare for virtio_ring transport feature bits, hook in a call in
all the users to manipulate them. This currently just clears all the
bits, since it doesn't understand any features.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Rather than explicitly handing the features to the lower-level, we just
hand the virtio_device and have it set the features. This make it clear
that it has the chance to manipulate the features of the device at this
point (and that all feature negotiation is already done).
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
We assign feature bits as required, but it makes sense to reserve some
for the particular transport, rather than the particular device.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
This patch enables virtio_console as the default console on kvm for
s390. We currently use the same notify hack as lguest for early
console output. I will try to address this for lguest and s390 later.
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
I also added a small Kconfig change that allows the user to specify the
virtio console in menuconfig.
(Fixes to export symbols from Stephen Rothwell <sfr@canb.auug.org.au>)
(Fixes for CONFIG_VIRTIO_CONSOLE=y vs CONFIG_VIRTIO=m from Christian himself)
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
This patch exploits the new notifier callbacks of the hvc_console. We can
use the virtio callbacks instead of the polling code.
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
This patch tries to change hvc_console to not use request_irq/free_irq if
the backend does not use irqs. This allows virtio_console to use hvc_console
without having a linker reference to request_irq/free_irq.
In addition, together with patch 2/3 it improves the performance for virtio
console input. (an earlier version of this patch was tested by Yajin on lguest)
The irq specific code is moved to hvc_irq.c and selected by the drivers that
use irqs (System p, System i, XEN).
I replaced "int irq" with the opaque "int data". The request_irq and
free_irq calls are replaced with notifier_add and notifier_del. I have also
changed the code a bit to call the notifier_add and notifier_del inside the
spinlock area as the callbacks are found via hp->ops.
Changes since last version:
o remove ifdef
o reintroduce "irq_requested" as "notified"
o cleanups, sparse..
I did not move the timer based polling into a separate polling scheme. I
played with several variants, but it seems we need to sleep/schedule in
a thread even for irq based consoles, as there are throttleing and buffer
size constraints.
I also kept hvc_struct defined in hvc_console.h so that hvc_irq.c can access
the irq_requested element.
Feedback is appreciated. virtio_console is currently the only available console
for kvm on s390. I plan to push this change as soon as all affected parties
agree on it. I would love to get test results from System p, Xen etc.
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Currently virtio_blk assumes a 512 byte hard sector size. This can cause
trouble / performance issues if the backing has a different block size
(like a file on an ext3 file system formatted with 4k block size or a dasd).
Lets add a feature flag that tells the guest to use a different hard sector
size than 512 byte.
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Hook up to the probe() and remove() methods in bus_type
rather than device_driver. The latter has been preferred
since 2.6.16.
Signed-off-by: Mark McLoughlin <markmc@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
We force notification when the ring is full, even if the host has
indicated it doesn't want to know. This seemed like a good idea at
the time: if we fill the transmit ring, we should tell the host
immediately.
Unfortunately this logic also applies to the receiving ring, which is
refilled constantly. We should introduce real notification thesholds
to replace this logic. Meanwhile, removing the logic altogether breaks
the heuristics which KVM uses, so we use a hack: only notify if there are
outgoing parts of the new buffer.
Here are the number of exits with lguest's crappy network implementation:
Before:
network xmit 7859051 recv 236420
After:
network xmit 7858610 recv 118136
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
If we hack the virtio_net driver to always allocate full-sized (64k+)
skbuffs, the driver slows down (lguest numbers):
Time to receive 1GB (small buffers): 10.85 seconds
Time to receive 1GB (64k+ buffers): 24.75 seconds
Of course, large buffers use up more space in the ring, so we increase
that from 128 to 2048:
Time to receive 1GB (64k+ buffers, 2k ring): 16.61 seconds
If we recycle pages rather than using alloc_page/free_page:
Time to receive 1GB (64k+ buffers, 2k ring, recycle pages): 10.81 seconds
This demonstrates that with efficient allocation, we don't need to
have a separate "small buffer" queue.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Finally this patch lets virtio_net receive GSO packets in addition
to sending them. This can definitely be optimised for the non-GSO
case. For comparison the Xen approach stores one page in each skb
and uses subsequent skb's pages to construct an SG skb instead of
preallocating the maximum amount of pages per skb.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> (added feature bits)
