On Fri, 18 Jan 2008 11:11:21 -0600 James Bottomley <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx> wrote: > > On Fri, 2008-01-18 at 08:52 -0800, Kristen Carlson Accardi wrote: > > On Thu, 17 Jan 2008 16:50:42 -0600 > > James Bottomley <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx> wrote: > > > > > On Tue, 2008-01-15 at 16:44 -0800, Kristen Carlson Accardi wrote: > > > > Add Enclosure Management support to libata and ahci. > > > > > > > > This patch adds support for the LED protocol, as defined in the > > > > AHCI spec. It adds a generic em_message and em_type sysfs entry > > > > per host. It also adds a sw_activity field per existing drive. > > > > > > > > The em_message field can be used by the driver to take enclosure > > > > management commands from userspace. In the case of the LED > > > > protocol, writes and reads from em_message correspond to the LED > > > > message format as defined in the AHCI spec. > > > > > > > > em_message type is a read only file that displays the current > > > > enclosure management protocol that is used by the driver. > > > > > > > > sw_activity is used by drivers which support software controlled > > > > activity LEDs. It has the following valid values: > > > > > > > > 0 OFF - the LED is not activated on activity > > > > 1 BLINK_ON - the LED blinks on every 10ms when activity > > > > is detected. 2 BLINK_OFF - the LED is on when idle, and > > > > blinks off every 10ms when activity is detected. > > > > > > > > It's important to note that the user must turn sw_activity OFF > > > > it they wish to control the activity LED via the em_message > > > > file. > > > > > > One of the things we really need to do is to get some type of > > > generic enclosure support. I note that ahci support three > > > standard eclosure management protocols (SAF-TE, SES-2, SFF-8485 > > > SGPIO) as well as the one proprietary one you've chosen to > > > implement. Is that because no-one in the field has actually > > > connected AHCI up to anything supporting one of the standard > > > protocols? > > > > > > I'm looking at this from slightly the other way around: the SAS > > > protocol is virtually mandating SFF-8485 as the enclosure > > > protocol to the point that it's actually built into the sas > > > management protocol ... I was starting to wonder how we should be > > > taking advantage of this. > > > > > > The implementation probably should be generic (above SCSI or IDE > > > or ATA) but it would obviously need to tap into the > > > subsytem/transport/device specific pieces, so possibly block > > > looks to be the right place to start? > > > > > > James > > > > > > > > > > I originally thought to try to make a generic enclosure management > > framework that we could hook individual EM protocols into. Then I > > started to wonder why we needed to add knowledge of these protocols > > into the kernel. At least the AHCI hardware which I'm familiar > > with, has no need to know anything about the protocol. It abstracts > > everything into just a message. So, the design that I did in this > > patch does the same thing. You export the type of protocol the > > driver is configured to accept, then the message buffer and leave > > it up to user space to understand the individual protocol. This > > works for all supported EM protocols. As far as I can see, most of > > these management protocols are better suited to being implemented > > in user space anyway. > > It's one way to look at it, if we go with SFF-8485 and the AHCI > specific protocol. Basically both of them are only about flashing > LEDs. The SAF-TE and SES protocols are much more comprehensive (and > include things like environmental monitors, temperature, fans, etc.). Even these though can be boiled down to read a message/write a message. > > I think SFF-8485 still needs the LED frequency generators for RAW > mode, so putting them in AHCI is a bit too low down. There's also the > question of a common user space interface for both. My reading of SFF-8485 leads me to believe that even in raw bit stream mode you are still just reading/writing message buffers. > > > As far as block, I'm not sure that makes sense, but maybe I'm > > misunderstanding what you want. The em message needs to be > > associated with the controller, not with individual devices. The > > reason for this is that the user may wish to locate a drive bay > > that has no disk in it, so they need to be able to send enclosure > > messages regardless of whether there's a block device associated > > with it. > > It's actually worse than that: enclosures aren't tied to HBAs even. > They're things that appear on Busses. Take FC as the logical extreme: > you can have tons of different enclosures on a single FC bus. For SATA they are tied to the controller. Maybe it's not feasible to come up with a solution that is generic to something like FC and SATA on the other end. > > But you can see from this, that enclosures are really separate devices > (separate from their contents or their connected HBA). > > The thought about block is basically that SGPIO is a frame in/frame > out protocol. It would probably have a raw interface via bsg a bit > like SMP does. However, I wouldn't necessarily tie it to block. It > would probably be tied to generic devices which get placed in the > device tree at appropriate locations. Ideally, we can place a SGPIO > enclosure device properly whether it's tied to SAS, FC or AHCI. > > James > > This seems like maybe something we could work on in an evolutionary way as the need presents itself. Honestly, without any SATA hardware that supports something beyond what this patch can support, it seems a lot of effort for little gain to try to share code, especially since the SATA devices wouldn't even use it. With both the AHCI and the nvidia EM solutions that are out there, that seems unneccessary. - 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
