When midi function is created, 'id' attribute is initialized with
SNDRV_DEFAULT_STR1, which is NULL pointer. Trying to read this attribute
before filling it ends up with segmentation fault.

This commit fix this issue by preventing null pointer dereference. Now
f_midi_opts_id_show() returns empty string when id is a null pointer.

Reproduction path:

$ mkdir functions/midi.0
$ cat functions/midi.0/id

[   53.130132] Unable to handle kernel NULL pointer dereference at
virtual address 00000000
[   53.132630] pgd = ec6cc000
[   53.135308] [00000000] *pgd=6b759831, *pte=00000000, *ppte=00000000
[   53.141530] Internal error: Oops: 17 [#1] PREEMPT SMP ARM
[   53.146904] Modules linked in: usb_f_midi snd_rawmidi libcomposite
[   53.153071] CPU: 1 PID: 2936 Comm: cat Not tainted
3.19.0-00041-gcf4b216 #7
[   53.160010] Hardware name: SAMSUNG EXYNOS (Flattened Device Tree)
[   53.166088] task: ee234c80 ti: ec764000 task.ti: ec764000
[   53.171482] PC is at strlcpy+0x8/0x60
[   53.175128] LR is at f_midi_opts_id_show+0x28/0x3c [usb_f_midi]
[   53.181019] pc : [<c0222a9c>]    lr : [<bf01bed0>]    psr: 60000053
[   53.181019] sp : ec765ef8  ip : 00000141  fp : 00000000
[   53.192474] r10: 00019000  r9 : ed7546c0  r8 : 00010000
[   53.197682] r7 : ec765f80  r6 : eb46a000  r5 : eb46a000  r4 :
ed754734
[   53.204192] r3 : ee234c80  r2 : 00001000  r1 : 00000000  r0 :
eb46a000
[   53.210704] Flags: nZCv  IRQs on  FIQs off  Mode SVC_32  ISA ARM
Segment user
[   53.217907] Control: 10c5387d  Table: 6c6cc04a  DAC: 00000015
[   53.223636] Process cat (pid: 2936, stack limit = 0xec764238)
[   53.229364] Stack: (0xec765ef8 to 0xec766000)
[   53.233706] 5ee0:
ed754734 ed7546c0
[   53.241866] 5f00: eb46a000 bf01bed0 eb753b80 bf01cc44 eb753b98
bf01b0a4 bf01b08c c0125dd0
[   53.250025] 5f20: 00002f19 00000000 ec432e00 bf01cce8 c0530c00
00019000 00010000 ec765f80
[   53.258184] 5f40: 00010000 ec764000 00019000 c00cc4ac ec432e00
c00cc55c 00000017 000081a4
[   53.266343] 5f60: 00000001 00000000 00000000 ec432e00 ec432e00
00010000 00019000 c00cc620
[   53.274502] 5f80: 00000000 00000000 00000000 00010000 ffff1000
00019000 00000003 c000e9a8
[   53.282662] 5fa0: 00000000 c000e7e0 00010000 ffff1000 00000003
00019000 00010000 00019000
[   53.290821] 5fc0: 00010000 ffff1000 00019000 00000003 7fffe000
00000001 00000000 00000000
[   53.298980] 5fe0: 00000000 be8c68d4 0000b995 b6f0e3e6 40000070
00000003 00000000 00000000
[   53.307157] [<c0222a9c>] (strlcpy) from [<bf01bed0>]
(f_midi_opts_id_show+0x28/0x3c [usb_f_midi])
[   53.316006] [<bf01bed0>] (f_midi_opts_id_show [usb_f_midi]) from
[<bf01b0a4>] (f_midi_opts_attr_show+0x18/0x24 )
[   53.327209] [<bf01b0a4>] (f_midi_opts_attr_show [usb_f_midi]) from
[<c0125dd0>] (configfs_read_file+0x9c/0xec)
[   53.337180] [<c0125dd0>] (configfs_read_file) from [<c00cc4ac>]
(__vfs_read+0x18/0x4c)
[   53.345073] [<c00cc4ac>] (__vfs_read) from [<c00cc55c>]
(vfs_read+0x7c/0x100)
[   53.352190] [<c00cc55c>] (vfs_read) from [<c00cc620>]
(SyS_read+0x40/0x8c)
[   53.359056] [<c00cc620>] (SyS_read) from [<c000e7e0>]
(ret_fast_syscall+0x0/0x34)
[   53.366513] Code: ebffe3d3 e8bd8008 e92d4070 e1a05000 (e5d14000)
[   53.372641] ---[ end trace e4f53a4e233d98d0 ]---

Signed-off-by: Pawel Szewczyk <p.szewczyk@samsung.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>

Replace a misspelled function name by %s and then __func__.

This was done using Coccinelle, including the use of Levenshtein distance,
as proposed by Rasmus Villemoes.

Signed-off-by: Julia Lawall <Julia.Lawall@lip6.fr>
Signed-off-by: Felipe Balbi <balbi@ti.com>

drivers/usb/gadget/function/f_midi.c:1072:21: sparse: symbol 'f_midi_alloc' was not declared. Should it be static?
drivers/usb/gadget/legacy/gmidi.c:118:30: sparse: symbol 'fi_midi' was not declared. Should it be static?
drivers/usb/gadget/legacy/gmidi.c:119:21: sparse: symbol 'f_midi' was not declared. Should it be static?

Signed-off-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>

Make the midi function available for gadgets composed with configfs.

Signed-off-by: Andrzej Pietrasiewicz <andrzej.p@samsung.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>

In order to add configfs support the usb_gstrings_attach must be used.

Signed-off-by: Andrzej Pietrasiewicz <andrzej.p@samsung.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>

There are no old f_midi interface users left, so remove it.

Signed-off-by: Andrzej Pietrasiewicz <andrzej.p@samsung.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>

Converting midi to the new function interface requires converting
the USB midi's function code and its users.

This patch converts the f_midi.c to the new function interface.
The file can now be compiled into a separate usb_f_midi.ko module.

The old function interface is provided by means of a preprocessor
conditional directives. After all users are converted, the old interface
can be removed.

Signed-off-by: Andrzej Pietrasiewicz <andrzej.p@samsung.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>

kstrdup() might fail, so check its return value and react appropriately.

Signed-off-by: Andrzej Pietrasiewicz <andrzej.p@samsung.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>

The soundcard index to use for the ALSA device creation is passed as a
parameter to f_midi_bind_config(), but is assigned to midi->index only
after the call to f_midi_register_card(midi). So no matter what is passed
to f_midi_bind_config(), the actual index for snd_card_new() is always 0.
This probably works ok if at the moment of f_midi's bind there are no
other snd_cards, but if there are, it is not possible to bind f_midi.

This patch moves the assignment to a place before the call to
f_midi_register_card(midi).

Signed-off-by: Andrzej Pietrasiewicz <andrzej.p@samsung.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>

The drivers/usb/gadget directory contains many files.
Files which are related can be distributed into separate directories.
This patch moves the USB functions implementations into a separate directory.

Signed-off-by: Andrzej Pietrasiewicz <andrzej.p@samsung.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>