leds: leds-gpio: reserve gpio before using it

leds: leds-gpio: reserve gpio before using it

This reverts commit a99d76f (leds: leds-gpio: use gpio_request_one)
and commit 2d7c22f (leds: leds-gpio: set devm_gpio_request_one()
flags param correctly) which was a fix of the first one.

The conversion to devm_gpio_request in commit e3b1d44c (leds:
leds-gpio: use devm_gpio_request_one) is not reverted.

The problem is that gpio_cansleep() and gpio_get_value_cansleep()
calls can crash if the gpio is not first reserved. Incidentally this
same bug existed earlier and was fixed similarly in commit d95cbe61
(leds: Fix potential leds-gpio oops). But the OOPS is real. It happens
when GPIOs are provided by module which is not yet loaded.

So this fixes the following BUG during my ALIX boot (3.9.2-vanilla):

BUG: unable to handle kernel NULL pointer dereference at 0000004c
IP: [<c11287d6>] __gpio_cansleep+0xe/0x1a
*pde = 00000000
Oops: 0000 [#1] SMP
Modules linked in: leds_gpio(+) via_rhine mii cs5535_mfd mfd_core
geode_rng rng_core geode_aes isofs nls_utf8 nls_cp437 vfat fat
ata_generic pata_amd pata_cs5536 pata_acpi libata ehci_pci ehci_hcd
ohci_hcd usb_storage usbcore usb_common sd_mod scsi_mod squashfs loop
Pid: 881, comm: modprobe Not tainted 3.9.2 #1-Alpine
EIP: 0060:[<c11287d6>] EFLAGS: 00010282 CPU: 0
EIP is at __gpio_cansleep+0xe/0x1a
EAX: 00000000 EBX: cf364018 ECX: c132b8b9 EDX: 00000000
ESI: c13993a4 EDI: c1399370 EBP: cded9dbc ESP: cded9dbc
 DS: 007b ES: 007b FS: 00d8 GS: 0033 SS: 0068
CR0: 8005003b CR2: 0000004c CR3: 0f0c4000 CR4: 00000090
DR0: 00000000 DR1: 00000000 DR2: 00000000 DR3: 00000000
DR6: ffff0ff0 DR7: 00000400
Process modprobe (pid: 881, ti=cded8000 task=cf094aa0 task.ti=cded8000)
Stack:
 cded9de0 d09471cb 00000000 c1399260 cf364014 00000000 c1399260 c1399254
 d0949014 cded9df4 c118cd59 c1399260 d0949014 d0949014 cded9e08 c118ba47
 c1399260 d0949014 c1399294 cded9e1c c118bb75 cded9e24 d0949014 00000000
Call Trace:
 [<d09471cb>] gpio_led_probe+0xba/0x203 [leds_gpio]
 [<c118cd59>] platform_drv_probe+0x26/0x48
 [<c118ba47>] driver_probe_device+0x75/0x15c
 [<c118bb75>] __driver_attach+0x47/0x63
 [<c118a727>] bus_for_each_dev+0x3c/0x66
 [<c118b6f9>] driver_attach+0x14/0x16
 [<c118bb2e>] ? driver_probe_device+0x15c/0x15c
 [<c118b3d5>] bus_add_driver+0xbd/0x1bc
 [<d08b4000>] ? 0xd08b3fff
 [<d08b4000>] ? 0xd08b3fff
 [<c118bffc>] driver_register+0x74/0xec
 [<d08b4000>] ? 0xd08b3fff
 [<c118c8e8>] platform_driver_register+0x38/0x3a
 [<d08b400d>] gpio_led_driver_init+0xd/0x1000 [leds_gpio]
 [<c100116c>] do_one_initcall+0x6b/0x10f
 [<d08b4000>] ? 0xd08b3fff
 [<c105e918>] load_module+0x1631/0x1907
 [<c10975d6>] ? insert_vmalloc_vmlist+0x14/0x43
 [<c1098d5b>] ? __vmalloc_node_range+0x13e/0x15f
 [<c105ec50>] sys_init_module+0x62/0x77
 [<c1257888>] syscall_call+0x7/0xb
EIP: [<c11287d6>] __gpio_cansleep+0xe/0x1a SS:ESP 0068:cded9dbc
CR2: 000000000000004c
 ---[ end trace 5308fb20d2514822 ]---

Signed-off-by: Timo Teräs <timo.teras@iki.f>
Cc: Sachin Kamat <sachin.kamat@linaro.org>
Cc: Raphael Assenat <raph@8d.com>
Cc: Trent Piepho <tpiepho@freescale.com>
Cc: Javier Martinez Canillas <javier.martinez@collabora.co.uk>
Cc: Arnaud Patard <arnaud.patard@rtp-net.org>
Cc: Ezequiel Garcia <ezequiel.garcia@free-electrons.com>
Acked-by: Jingoo Han <jg1.han@samsung.com>
Signed-off-by: Bryan Wu <cooloney@gmail.com>