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SubjectRe: [PATCH] ide: ide_port_wait_ready() fix
From
From: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
Date: Thu, 13 Oct 2011 12:41:04 +0200

> David Miller wrote:
>
>> From: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
>> Date: Wed, 12 Oct 2011 16:59:55 +0200
>>
>> > David Miller wrote:
>> >
>> >> From: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
>> >> Date: Tue, 11 Oct 2011 19:13:18 +0200
>> >>
>> >> > From: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
>> >> > Subject: [PATCH] ide: ide_port_wait_ready() fix
>> >> >
>> >> > Fix for commit a20b2a4 ("ide: skip probe if there are no devices on
>> >> > the port (v2)"). We must check for slave device before failing.
>> >> >
>> >> > Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
>> >>
>> >> This will mishandle the case where there is no slave in the device
>> >> list.
>> >
>> > I don't see it:
>> >
>> > @ -598,7 +598,7 @@ static int ide_port_wait_ready(ide_hwif_
>> > {
>> > const struct ide_tp_ops *tp_ops = hwif->tp_ops;
>> > ide_drive_t *drive;
>> > - int i, rc;
>> > + int i, rc, prev_rc = 0;
>> >
>> > printk(KERN_DEBUG "Probing IDE interface %s...\n", hwif->name);
>> >
>> > @@ -623,8 +623,10 @@ static int ide_port_wait_ready(ide_hwif_
>> > tp_ops->write_devctl(hwif, ATA_DEVCTL_OBS);
>> > mdelay(2);
>> > rc = ide_wait_not_busy(hwif, 35000);
>> > - if (rc)
>> > + if (prev_rc && rc)
>> > goto out;
>> > + prev_rc = rc;
>> > + rc = 0;
>> > } else
>> > printk(KERN_DEBUG "%s: ide_wait_not_busy() skipped\n",
>> > drive->name);
>> >
>> > If there is no slave device but there is a master device the code falls-through
>> > and returns a success.
>>
>> That's not what we want, if there is only a master device and no slave device
>> in the list this loop is iterating over we want to return the error code
>> in "rc", not zero.
>
> No, we want to return zero (success) since at least once device was found
> (otherwise we fail probe on some esoteric setups returning -ENODEV from
> ide_wait_not_busy() for master device).
>
> This is how this function worked before commit a20b2a4 if you want something
> else okay but it needs to work with aforementioned setups.

You unconditionally assign "prev_rc = rc" and set "rc = 0" so if we only run
the loop once, we return zero.

And we do this even if that one device gave a non-zero return value.

That's not what we want.


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