On Tue, 23 Feb 2010, Ramya Desai wrote:
> On Mon, Feb 22, 2010 at 11:14 PM, Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote:
>
> Dear Alan,
>
> Thanks for the information.
>
> > Usb-storage sets max_sectors to 240 in the host template. For some
> > reason, the block layer also changes max_hw_sectors to the same value
> > (see block/blk-settings.c:blk_queue_max_sectors()).
>
> I am setting the max_sectors in host template (scsiglue.c file). When
> the max_sectors value is <= 1024, then only the max_sectors_kb and
> max_hw_sectors_kb are same in the sys interface. However, if the
> max_sectors value is > 1024 then the values in the sys interface files
> are different as shown in block/blk-setting.c:blk_queue_max_sectors().
>
> if (BLK_DEF_MAX_SECTORS > max_sectors)
> q->limits.max_hw_sectors = q->limits.max_sectors = max_sectors;
> else {
> q->limits.max_sectors = BLK_DEF_MAX_SECTORS;
> q->limits.max_hw_sectors = max_sectors;
> }
James or Jens, is there a reason why this routine limits max_sectors to
1024?
And is there a reason why it sets both max_sectors and max_hw_sectors,
leaving no way to change one without the other?
Are drivers supposed to assign values directly to
q->limits.max_sectors? Shouldn't there be a cleaner API for all this?
Alan Stern
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