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Removable flash storage

DISCUSSION Brad Beveridge 1 participant 2 messages Nov 17, 2004 1 message not in the archive Memory technology devices (MTD)

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Brad Beveridge

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Hello all.
I am working with a device that has 3 nand flash slots, two are internal and not removable, one is external and is removable.
We currently have a single driver that registers partitions on each card at kernel boot time. All three cards work, and we use yaffs as a filesystem on top of MTD.
I am trying to come up with a clean way of allowing the external card to be inserted/removed at runtime.
One solution is to have a seperate nand driver for that card & build it as a module, then simply modprobe/rmmod. However, that solution isn't so great because we then have two driver source files that are essentially the same. We also thought that a /proc based solution might work, where you write "eject 3" or something to /proc/mtd.

What will play nicest with MTD as it stands? If I need to break the driver up, is there any suggestions for minimising code duplication?

Cheers
Brad

A message that is not in the archive (sent off-list or not yet received): [email protected]

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Looks like I sent a message that didn't hit the list. It is attached below.

More info - having a single partition on my NAND device causes no oops. But multiple (3) partitions on the nand device does cause it to break.

From a quick look in mtdpart.c, it looks like when you add a partition, slave->master is always set to master. Automatically adding/deleting mtd devices looks like it is killing me somehow. Any suggestions on what I should do to tell mtd and nand_release that only one device should be deleted for all 3 partitions?

Cheers
Brad

Quoted 87 lines · Brad Beveridge

Hi again. Further to my previous post, I am finding that when I rmmod my nand module, I get a kernel oops (see below).
When I insmod my driver, basically I do some setup & call nand_scan, then if that returns OK I call add_mtd_partitions.
On rmmod, I simply call nand_release, then kfree my mtd_info structure. I've only started looking into this, but I thought I should post the oops output so wiser heads could take a look. Ang suggestions on how to start tracking down this particular oops?

Cheers
Brad

Here is the oops output

kernel BUG at include/linux/dcache.h:276!

Unable to handle kernel NULL pointer dereference at virtual address 00000000
pgd = c5864000
[00000000] *pgd=a5cd1011, *pte=00000000, *ppte=00000000
Internal error: Oops: 807 [#1]
Modules linked in: scallop
CPU: 0
PC is at __bug+0x40/0x54
LR is at 0x1
pc : [<c0028bec>]    lr : [<00000001>]    Not tainted

sp : c5e9ddd8 ip : 60000093 fp : c5e9dde8
r10: befffe64 r9 : c5e9c000 r8 : c02a1400
r7 : c01dabc0 r6 : c01dab7c r5 : c587b948 r4 : 00000000 r3 : 00000000 r2 : 00000000 r1 : 00001596 r0 : 00000001
Flags: nZCv IRQs on FIQs on Mode SVC_32 Segment user
Control: 397F Table: A5864000 DAC: 00000015 Process rmmod (pid: 43, stack limit = 0xc5e9c190)

Stack: (0xc5e9ddd8 to 0xc5e9e000)

ddc0: c5c5dd60 c5e9de00
dde0: c5e9ddec c00a1840 c0028bb8 c5c5dd60 c026a380 c5e9de14 c5e9de04 c00d9028
de00: c00a1820 c5c5dd60 c5e9de28 c5e9de18 c00d904c c00d9010 c5c5dd10 c5e9de3c
de20: c5e9de2c c01127fc c00d9044 c5c5dd10 c5e9de54 c5e9de40 c0116bdc c01127e8
de40: c026a380 c026a380 c5e9de68 c5e9de58 c0117970 c0116bb8 00000000 c5e9de80
de60: c5e9de6c c00a0a0c c0117968 c031b920 c01daba8 c5e9de94 c5e9de84 c012f37c
de80: c00a09ac c031b920 c5e9dea8 c5e9de98 c012e9f4 c012f2e4 c01dabb0 c5e9decc
dea0: c5e9deac c012f3f4 c012e9ec c01dabe8 c02a1400 c01daaec c01daadc c021b468
dec0: c5e9def0 c5e9ded0 c012b62c c012f3ac c01daaf4 c02a1400 c01daaf4 c5880c00
dee0: 00000880 c5e9df10 c5e9def4 c012c818 c012b5a4 c5880c00 c5880d68 c01cf184
df00: c5e9df48 c5e9df28 c5e9df14 c0132f38 c012c7d8 00000002 bf001580 c5e9df40
df20: c5e9df2c bf0007b8 c0132f2c bf001480 00000000 c5e9dfa4 c5e9df44 c004cf20
df40: bf00077c 00000000 6c616373 00706f6c c0060fb0 c5ee428c c5c60640 60000010
df60: c5e9c000 4019cbe0 c5ee428c c5e9dfac c5e9df7c c0029e88 c00dab58 c5e9dfac
df80: 00000000 6c616373 00706f6c 000741c8 00000081 c00232a4 00000000 c5e9dfa8
dfa0: c0023120 c004cd68 00706f6c 000741c8 00900081 befffe5c 00000880 00000000
dfc0: 6c616373 00706f6c 000741c8 00000002 00000880 00000000 befffe64 befffe8c
dfe0: befffe5c befffe50 0002cf10 4019cbf0 60000010 00900081 0000b990 0000b990

Backtrace:
[<c0028bac>] (__bug+0x0/0x54) from [<c00a1840>] (sysfs_remove_dir+0x2c/0x168)

r4 = C5C5DD60
[<c00a1814>] (sysfs_remove_dir+0x0/0x168) from [<c00d9028>] (kobject_del+0x24/0x34) r5 = C026A380 r4 = C5C5DD60
[<c00d9004>] (kobject_del+0x0/0x34) from [<c00d904c>] (kobject_unregister+0x14/0x20) r4 = C5C5DD60
[<c00d9038>] (kobject_unregister+0x0/0x20) from [<c01127fc>] (elv_unregister_queue+0x20/0x30) r4 = C5C5DD10
[<c01127dc>] (elv_unregister_queue+0x0/0x30) from [<c0116bdc>] (blk_unregister_queue+0x30/0x48) r4 = C5C5DD10
[<c0116bac>] (blk_unregister_queue+0x0/0x48) from [<c0117970>] (unlink_gendisk+0x14/0x28) r5 = C026A380 r4 = C026A380
[<c011795c>] (unlink_gendisk+0x0/0x28) from [<c00a0a0c>] (del_gendisk+0x6c/0xc4)
r4 = 00000000
[<c00a09a0>] (del_gendisk+0x0/0xc4) from [<c012f37c>] (del_mtd_blktrans_dev+0xa4/0xc8) r5 = C01DABA8 r4 = C031B920
[<c012f2d8>] (del_mtd_blktrans_dev+0x0/0xc8) from [<c012e9f4>] (mtdblock_remove_dev+0x14/0x20) r4 = C031B920
[<c012e9e0>] (mtdblock_remove_dev+0x0/0x20) from [<c012f3f4>] (blktrans_notify_remove+0x54/0x84) r4 = C01DABB0
[<c012f3a0>] (blktrans_notify_remove+0x0/0x84) from [<c012b62c>] (del_mtd_device+0x94/0xf0) r8 = C021B468 r7 = C01DAADC r6 = C01DAAEC r5 = C02A1400
r4 = C01DABE8
[<c012b598>] (del_mtd_device+0x0/0xf0) from [<c012c818>] (del_mtd_partitions+0x4c/0x70) r8 = 00000880 r7 = C5880C00 r6 = C01DAAF4 r5 = C02A1400
r4 = C01DAAF4
[<c012c7cc>] (del_mtd_partitions+0x0/0x70) from [<c0132f38>] (nand_release+0x18/0x58) r7 = C5E9DF48 r6 = C01CF184 r5 = C5880D68 r4 = C5880C00
[<c0132f20>] (nand_release+0x0/0x58) from [<bf0007b8>] (scallop_cleanup+0x48/0x94 [scallop]) r5 = BF001580 r4 = 00000002
[<bf000770>] (scallop_cleanup+0x0/0x94 [scallop]) from [<c004cf20>] (sys_delete_module+0x1c4/0x228) r5 = 00000000 r4 = BF001480
[<c004cd5c>] (sys_delete_module+0x0/0x228) from [<c0023120>] (ret_fast_syscall+0x0/0x2c) r8 = C00232A4 r7 = 00000081 r6 = 000741C8 r5 = 00706F6C
r4 = 6C616373

Code: 1b003adb e59f0014 eb003ad9 e3a03000 (e5833000)

Segmentation fault

<--- end of oops -->

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Bluewater Systems Ltd - ARM Technology Solution Centre

      Brad Beveridge                           Bluewater Systems Ltd
Phone: +64 3 3779127 (Aus +1 800 148 751)       Level 17, 119 Armagh St
Fax:   +64 3 3779135                            PO Box 13889
Email: [email protected]              Christchurch
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