On 12 August 2016 at 21:42, Sergei Shtylyov
[off-list ref] wrote:

On 08/12/2016 02:56 PM, tom.ty89@gmail.com wrote:

quoted

From: Tom Yan <redacted>

Currently we use dev->max_sectors to set max_hw_sectors, which
is actually supposed to be a host controller limit (that get set

   Gets.

Thanks, but I read too late. I'll try to bare in mind to correct that
if I'll need to send a v3 or so.

quoted

diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c
index be9c76c..4e2d8e7 100644
--- a/drivers/ata/libata-scsi.c
+++ b/drivers/ata/libata-scsi.c

@@ -1204,14 +1204,26 @@ static int ata_scsi_dev_config(struct scsi_device

*sdev,
        if (!ata_id_has_unload(dev->id))
                dev->flags |= ATA_DFLAG_NO_UNLOAD;

-       /* configure max sectors */
-       blk_queue_max_hw_sectors(q, dev->max_sectors);
-
        if (dev->class == ATA_DEV_ATAPI) {
                void *buf;

                sdev->sector_size = ATA_SECT_SIZE;

+               /*
+                * We are setting the limit here merely because CD/DVD
device does not
+                * have Block Limits VPD.
+                *
+                * Supposedly dev->max_sectors should be left shifted by
+                * (ilog2(sdev->sector_size) - 9). But since ATAPI class
device has a
+                * static logical sector size of 512 (ATA_SECT_SIZE), the
shift became
+                * unnecessary.
+                */
+               q->limits.max_dev_sectors = dev->max_sectors;
+               /* Make max_dev_sectors effective by adjusting max_sectors
accordingly,
+                  while leave max_hw_sectors, which is supposed to be
host controller
+                  limit, untouched. */

   Why 2 different comment styles? The previous comment's style is actually
preferred in the kernel.

I just tried to follow the styles of the existing comments. Apparently
the first style is used for multi-paragraph comments, while the other
one is used for single-paragraph one.