On Mon, Jan 3, 2011 at 2:30 PM, Peter M. Petrakis <peter.petrakis@xxxxxxxxxxxxx> wrote: > Hi, > > On 12/30/2010 10:58 AM, Greg Freemyer wrote: >> All, >> >> Per T13/1699-D Revision 4a (from May 2007) word 217 of the identify >> block should be populated with a "1" to identify non-rotating media. >> >> http://www.t13.org/Documents/UploadedDocuments/docs2007/D1699r4a-ATA8-ACS.pdf >> >> Does anyone know if that is a reliable field? >> >> Specifically there are two separate issues: >> >> 1) Are all devices reporting a 1 in field 217 non-rotating? >> 2) Are all production non-rotating devices populating that field with a 1. >> >> Is there some other reliable mechanism for identifying a SSD? >> > > Not really, the manufacturer needs to adhere to the spec they're claiming > to honor and we should politely notify them when we find that it's inconsistent. > It's technically a firmware bug if it's ATA-8 and that bit isn't set right. > > If you're having trouble identifying SSDs pre ATA-8, you can use this simple > patch I introduced a while back. > > http://www.spinics.net/lists/linux-ide/msg38944.html > > and blacklist the offending drive into reporting itself as SSD when interrogated > via SCSI. > > If you search around, you'll find an earlier thread about quirking SSDs by using > heuristics like search for the word "flash" in the device name and other hints but > the patch set never went anywhere. It's a ugly problem, there's so many devices > out there ahead of the spec that are SSD, with no sure fire way to determine that > they really are. Supporting a full blacklist of them would turn libata-core.c into > a dumping ground for potentially 100s of pre ATA-8 storage devices. I don't think > anyone wants to maintain that. > > Peter Peter, Thanks. I have a client that needs to recognize SSDs from userspace and I missed the ABI. I was looking for the userspace ABI to be in /sys/block like the topology stuff is, so I missed the userspace ABI and was confused. Now that I've found in, I'm confused by ata_id_rotation_rate() trusting the rotation_rate of 1 being valid for all ATA 7 and ATA 8 devices. === cut & paste from ata.h static inline int ata_id_rotation_rate(const u16 *id) { u16 val = id[217]; if (ata_id_major_version(id) < 7 || val == 0 || val == 0xffff) return 0; if (val > 1 && val < 0x401) return 0; return val; } === I thought rotational_rate set to 1 to indicate a SSD was only valid for ATA8 devices? I'll have to go back and read the older thread you talked about, but is there a plan for ATA7 devices? Is it in general to trust word 217, or what. If I find a SSD device that is not setting word 217 correctly, and I want to get the kernel to address it correctly, should I just add to your list and cause ATA_HORKAGE_NONROT to be set? Or is the concern it will get unwieldy too fast if everyone used that list? Thanks Greg -- To unsubscribe from this list: send the line "unsubscribe linux-ide" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
