Re: [PATCH 4/6] ata: fixup ATA_PROT_NODATA

[Hannes Reinecke <hare@suse.de>]

On 06/20/2016 05:44 PM, Tejun Heo wrote:
> On Mon, Jun 20, 2016 at 01:39:14PM +0200, Hannes Reinecke wrote:
>> The taskfile protocol is a numeric value, and can not be ORed.
>>
>> Signed-off-by: Hannes Reinecke <hare@suse.de>
>> ---
>>  drivers/ata/libata-core.c | 4 ++--
>>  drivers/ata/libata-eh.c   | 2 +-
>>  2 files changed, 3 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
>> index e798915..d200102 100644
>> --- a/drivers/ata/libata-core.c
>> +++ b/drivers/ata/libata-core.c
>> @@ -1238,7 +1238,7 @@ static int ata_read_native_max_address(struct ata_device *dev, u64 *max_sectors)
>>  	} else
>>  		tf.command = ATA_CMD_READ_NATIVE_MAX;
>>  
>> -	tf.protocol |= ATA_PROT_NODATA;
>> +	tf.protocol = ATA_PROT_NODATA;
>>  	tf.device |= ATA_LBA;
> 
> Did the above lead to any actual brekage or was tf.protocol guaranteed
> to be zero always?  I wish the patch description described what the
> stake of the patch is.
> 
This is actually a cleanup; if tf.protocl is '0' we won't see any issues
here.
But if (for some obsure reason) tf.protocol is _not_ zero we'll run into
very obscure problems.
Plus the OR here might give others the wrong impression, and might lead
to a confusion between ATA_PROT_XXX (which is a scalar value and cannot
be ORed) and ATA_PROT_FLAG_XXX (which is a bit value and can be ORed).

Cheers,

Hannes
-- 
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