Messages in this thread | | | From | David Brownell <> | Subject | Re: [PATCH] gpiolib: fix oops on reading sysfs exported GPIOs | Date | Thu, 16 Oct 2008 08:43:08 -0700 |
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On Thursday 16 October 2008, Anton Vorontsov wrote:
> Oops: Kernel access of bad area, sig: 11 [#1] > [...] > NIP [00000000] 0x0 > LR [c0182fb0] gpio_get_value_cansleep+0x40/0x50 > Call Trace: > [c7b79e80] [c0183f28] gpio_value_show+0x5c/0x94 > [c7b79ea0] [c01a584c] dev_attr_show+0x30/0x7c > [c7b79eb0] [c00d6b48] fill_read_buffer+0x68/0xe0 > [c7b79ed0] [c00d6c54] sysfs_read_file+0x94/0xbc > [c7b79ef0] [c008f24c] vfs_read+0xb4/0x16c > [c7b79f10] [c008f580] sys_read+0x4c/0x90 > [c7b79f40] [c0013a14] ret_from_syscall+0x0/0x38
Rude. But notice it's not unique to the sysfs path. Trying to fix only the sysfs path allows oosping in other cases.
> GPIO users should always issue the gpio_direction_input() call and > check its return value prior to trying gpio_get_value().
Not true; the API explicitly allows GPIOs to be treated as bidirectional, even when they're configured as outputs. That's because most GPIOs *are* bidirectional.
See the better patch in my next message.
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