[PATCH libata: add SSD detection hueristic; move SSD setup to ata_dev_configure (was Re: [GIT PULL] Ext3 latency fixes)



Linus Torvalds wrote:

On Mon, 6 Apr 2009, Jeff Garzik wrote:

Arjan van de Ven wrote:
On Sun, 05 Apr 2009 16:57:21 -0400
Jeff Garzik <jeff@xxxxxxxxxx> wrote:
We set it in libata-scsi.c:ata_scsi_dev_config() based on
ata_id_is_ssd()

That hueristic probably assumes Intel SSDs or something :/
you mean the "rpm" set to '1' ?
I was pretty sure that that was industry standard...
A -new- industry standard. You can certainly create a compliant SSD while
only conforming to ATA-7, for example. Some older IDE flash devices pretend
they are normal hard drives in almost every respect, too.

Something like this might be a good idea.

I've seen several SSD's that do _not_ do that whole RPM == 1 thing, but they have "SSD" in their names.

I forget how the ID is stored (I have this memory of it being big-endian 16-bit words or something crazy like that?), but aside from fixing up that kind of crazyness, maybe something like this is worth it?

And making it non-inline, of course. And maybe it should use 'strstr()' instead of checking whether the name ends in 'SSD'. You get the idea..

ata_id_string() or ata_id_c_string() is what you want.

But yeah, we see what you're trying to illustrate.

For internal reasons, it is better to detect and set up SSD details in ata_dev_configure(), where we detect and configure other ATA details.

I've attached an example patch, compiled-tested only.

If we wanted to get more fancy, we could extend the strn_pattern_cmp() function in libata to accept wildcard '*' prefixes, as well as suffixes. That would make it easy to auto-configure future ATA devices based on the product id (such as "G.SKILL 128GB SSD").

Jeff


diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
index e7ea77c..3043a61 100644
--- a/drivers/ata/libata-core.c
+++ b/drivers/ata/libata-core.c
@@ -2411,6 +2411,8 @@ int ata_dev_configure(struct ata_device *dev)

/* ATA-specific feature tests */
if (dev->class == ATA_DEV_ATA) {
+ char *model_suffix;
+
if (ata_id_is_cfa(id)) {
if (id[162] & 1) /* CPRM may make this media unusable */
ata_dev_printk(dev, KERN_WARNING,
@@ -2438,6 +2440,13 @@ int ata_dev_configure(struct ata_device *dev)
dev->multi_count = cnt;
}

+ if (strlen(modelbuf) <= 3)
+ model_suffix = modelbuf;
+ else
+ model_suffix = modelbuf + (strlen(modelbuf) - 3);
+ if (ata_id_is_ssd(id) || !strcmp(model_suffix, "SSD"))
+ dev->flags |= ATA_DFLAG_NONROT;
+
if (ata_id_has_lba(id)) {
const char *lba_desc;
char ncq_desc[20];
diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c
index b9747fa..e597a4f 100644
--- a/drivers/ata/libata-scsi.c
+++ b/drivers/ata/libata-scsi.c
@@ -1097,7 +1097,7 @@ static int ata_scsi_dev_config(struct scsi_device *sdev,

blk_queue_dma_drain(q, atapi_drain_needed, buf, ATAPI_MAX_DRAIN);
} else {
- if (ata_id_is_ssd(dev->id))
+ if (dev->flags & ATA_DFLAG_NONROT)
queue_flag_set_unlocked(QUEUE_FLAG_NONROT,
sdev->request_queue);

diff --git a/include/linux/libata.h b/include/linux/libata.h
index b450a26..a0fdbf0 100644
--- a/include/linux/libata.h
+++ b/include/linux/libata.h
@@ -147,6 +147,7 @@ enum {
ATA_DFLAG_SLEEPING = (1 << 15), /* device is sleeping */
ATA_DFLAG_DUBIOUS_XFER = (1 << 16), /* data transfer not verified */
ATA_DFLAG_NO_UNLOAD = (1 << 17), /* device doesn't support unload */
+ ATA_DFLAG_NONROT = (1 << 18), /* is non-rotational media, SSD */
ATA_DFLAG_INIT_MASK = (1 << 24) - 1,

ATA_DFLAG_DETACH = (1 << 24),