Re: [PATCH v9 03/10] ata: zpodd: identify and init ZPODD devices

[Aaron Lu <aaron.lu@intel.com>]

On 11/18/2012 10:38 PM, Tejun Heo wrote:
> Hello, Aaron.
Hi,

> 
> On Wed, Nov 14, 2012 at 09:32:27AM +0800, Aaron Lu wrote:
>>> I don't think you're supposed to use dev->private_data from libata
>>> core layer.  Just add a new field.  Nobody cares about adding 8 more
>>> bytes to struct ata_device and spending 8 more bytes is way better
>>> than muddying the ownership of ->private_data.
>>
>> OK.
>> And just out of curiosity, who's supposed to use device's private_data?
>> I didn't find any user for ata_device's private_data in libata.
> 
> All the ->private_data fields are to be used by low level drivers
> (ahci, ata_piix, pata_via...).  Given the twisted nature of ATA
> devices, it's a bit surprising that no driver yet found a need for
> ata_dev->private_data.  For most SATA controllers, port to device is
> one to one so maybe ap->private_data is enough.
> 
>>> And this gets completely wrong.  What if the device supports DA and
>>> low level driver makes use of ->private_data?
>>
>> I didn't find any user of ata_device's private_data, so I used it for
>> ZPODD. But if this is dangerous, I'll use a new field.
> 
> As there currently is no other user, it won't break anything but yeah
> please add a properly typed and named field.

OK, and thanks for the suggestion.

-Aaron

> 
> Thanks.
>