Messages in this thread | | | Subject | Re: [PATCH] drivers/ata: print trim features at device initialization | From | Konstantin Khlebnikov <> | Date | Mon, 10 Jun 2019 10:49:01 +0300 |
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On 10.06.2019 0:37, James Bottomley wrote: > On Sat, 2019-06-08 at 17:13 +0300, Konstantin Khlebnikov wrote: >>> On 08.06.2019 11:25, Christoph Hellwig wrote:> On Fri, Jun 07, 2019 >>> at 10:34:39AM +0300, Konstantin Khlebnikov wrote: >>> > >>> > Do we really need to spam dmesg with even more ATA crap? What >>> about >>> > a sysfs file that can be read on demand instead? >>> > >>> >>> Makes sense. >>> >>> Trim state is exposed for ata_device: >>> /sys/class/ata_device/devX.Y/trim >>> but there is no link from scsi device to ata device so they hard to >>> match. >>> >>> I'll think about it. >> >> Nope. There is no obvious way to link scsi device with ata_device. >> ata_device is built on top of "transport_class" and >> "attribute_container". >> This some extremely over engineered sysfs framework used only in >> ata/scsi. I don't want to touch this. > > You don't need to know any of that. The problem is actually when the > ata transport classes were first created, the devices weren't properly > parented. What should have happened, like every other transport class, > is that the devices should have descended down to the scsi device as > the leaf in an integrated fashion. Instead, what we seem to have is > three completely separate trees. > > So if you look at a SAS device, you see from the pci device: > > host2/port-2:0/end_device-2:0/target2:0:0/2:0:0:0/block/sdb/sdb1 > > But if you look at a SATA device, you see three separate paths: > > ata3/host3/target3\:0\:0/3\:0\:0\:0/block/sda/sda1 > ata3/link3/dev3.0/ata_device/dev3.0 > ata3/ata_port/ata3 > > Instead of an integrated tree > > Unfortunately, this whole thing is unfixable now. If I integrate the > tree properly, the separate port and link directories will get subsumed > and we won't be able to recover them with judicious linking so scripts > relying on them will break. The best we can probably do is add > additional links with what we have. > > To follow the way we usually do it, there should be a link from the ata > device to the scsi target, but that wouldn't help you find the "trim" > files, so it sounds like you want a link from the scsi device to the ata device, which would?
Yes, I'm talking about link from scsi device to leaf ata_device node.
In libata scsi_device has one to one relation with ata_device. So making link like /sys/class/block/sda/device/ata_device should be possible easy. But I haven't found implicit reference from struct ata_device to ata_device in sysfs.
In simplest ahci case whole path looks like: /sys/devices/pci0000:00/0000:00:1f.2/ata1/link1/dev1.0/ata_device/dev1.0 |______________________|__ata_host__|port|link_|_tdev_|___ata_device___|
/sys/class/ata_device/dev1.0 points directly to leaf ata_device While in struct ata_device tdev is different intermediate node.
It would be nice merge tdev and ata_device into one node, or at least embed leaf struct device into struct ata_device too.
As I see ata registers only "transport" device while scsi transport template magically matches it and creates actual ata device of ata_dev_class. I see no reason for this complexity. Why ata host couldn't enumerate and register all these devices explicitly?
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