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Date: Thu, 21 May 2015 12:17:15 +0200
From: Richard Weinberger <richard@nod.at>
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To: Brian Norris <computersforpeace@gmail.com>
Subject: Re: [PATCH] mtd: blktrans: change blktrans_getgeo rerurn value
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Cc: David Woodhouse <dwmw2@infradead.org>,
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Am 21.05.2015 um 10:05 schrieb Brian Norris:
> On Thu, May 21, 2015 at 09:56:21AM +0200, Richard Weinberger wrote:
>> On Wed, May 20, 2015 at 9:33 PM, Brian Norris
>> <computersforpeace@gmail.com> wrote:
>>> On Wed, May 13, 2015 at 02:29:16PM +0800, Wenlin Kang wrote:
>>>> Modify function blktrans_getgeo()'s return value to -ENXIO when
>>>> dev->tr->getgeo == NULL.
>>>>
>>>> We shouldn't make the return value to 0 when dev->tr->getgeo == NULL,
>>>> because the function blktrans_getgeo() has an output value "hd_geometry"
>>>> which is usually used by some application, if return 0, it will make some
>>>> application get the wrong information.
>>>>
>>>> Signed-off-by: Wenlin Kang <wenlin.kang@windriver.com>
>>>> ---
>>>>  drivers/mtd/mtd_blkdevs.c |    2 +-
>>>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>>>
>>>> diff --git a/drivers/mtd/mtd_blkdevs.c b/drivers/mtd/mtd_blkdevs.c
>>>> index 2b0c5287..f8bb16e 100644
>>>> --- a/drivers/mtd/mtd_blkdevs.c
>>>> +++ b/drivers/mtd/mtd_blkdevs.c
>>>> @@ -273,7 +273,7 @@ static int blktrans_getgeo(struct block_device *bdev, struct hd_geometry *geo)
>>>>       if (!dev->mtd)
>>>>               goto unlock;
>>>>
>>>> -     ret = dev->tr->getgeo ? dev->tr->getgeo(dev, geo) : 0;
>>>> +     ret = dev->tr->getgeo ? dev->tr->getgeo(dev, geo) : -ENXIO;
>>>
>>> Good catch. I don't think ENXIO is correct in this case, though. Maybe
>>> -EOPNOTSUPP or -ENOSYS? The latter might make more sense I guess.
>>
>> I'd vote for -ENOTTY as this is what HDIO_GETGEIO returns
>> if the function is not implemented and blktrans_getgeo()
>> is only a wrapper around that.
> 
> I suppose that makes more sense.
> 
>> See https://www.kernel.org/doc/Documentation/ioctl/hdio.txt
> 
> But this only mentions EINVAL...

Because ENOTTY is covered by ioctl().
If you request a non-existing function this error code will
be returned.

Thanks,
//richard