Re: [PATCH 5 of 8] sd: Detect non-rotational devices

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Jens Axboe wrote:
On Thu, Apr 23 2009, Jeff Garzik wrote:
Jens Axboe wrote:
+static void sd_read_block_characteristics(struct scsi_disk *sdkp)
+{
+	char *buffer;
+	u16 rot;
+
+	/* Block Device Characteristics VPD */
+	buffer = scsi_get_vpd_page(sdkp->device, 0xb1);
+
+	if (buffer == NULL)
+		return;
+
+	rot = get_unaligned_be16(&buffer[4]);
+
+	if (rot == 1)
+		queue_flag_set_unlocked(QUEUE_FLAG_NONROT, sdkp->disk->queue);
+
+	kfree(buffer);
+}
+
+/**
  *	sd_revalidate_disk - called the first time a new disk is seen,
  *	performs disk spin up, read_capacity, etc.
  *	@disk: struct gendisk we care about
@@ -1836,6 +1860,7 @@ static int sd_revalidate_disk(struct gen
 	 */
 	if (sdkp->media_present) {
 		sd_read_capacity(sdkp, buffer);
+		sd_read_block_characteristics(sdkp);
 		sd_read_write_protect_flag(sdkp, buffer);
 		sd_read_cache_type(sdkp, buffer);
 		sd_read_app_tag_own(sdkp, buffer);
@@ -1976,6 +2001,8 @@ static void sd_probe_async(void *data, a
 	add_disk(gd);
 	sd_dif_config_host(sdkp);
 +	sd_revalidate_disk(gd);
+
 	sd_printk(KERN_NOTICE, sdkp, "Attached SCSI %sdisk\n",
 		  sdp->removable ? "removable " : "");
Make sure this works for libata as well, and then kill the rotational
check in there instead.
Yep.  libata-scsi.c would need to simulate that VPD page.

Exactly

Also (to mkp or whoever does the work) -- note Linus's comment, and my provisional patch[1], about libata potentially wanting to detect NONROT by looking for "*SSD" from IDENTIFY DEVICE'S model string.

I think that's an entirely orthogonal issue.

Yes.

If somebody is going to be essentially rewriting the libata SSD detection logic, that area will get stirred _anyway_.

So I hope it is not out of bounds to point out additional areas where a developer could serve a legitimate need of Linux users, particularly when doing so is easy and a provisional patch already exists.

	Jeff



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