On 22 August 2016 at 08:31, Tom Yan <tom.ty89@xxxxxxxxx> wrote: > As mentioned before, as of the latest draft of ACS-4, nothing about a > larger payload size is mentioned. Conservatively speaking, it sort of *payload block size > means that we are allowing four 512-byte block payload on 4Kn device *eight 512-byte-block payload > regardless of the reported limit in the IDENTIFY DEVICE data. I am > really not sure if it's a good thing to do. Doesn't seem necessary > anyway, especially when our block layer does not support such a large > bio size (well, yet), so each request will end up using a payload of > two 512-byte blocks at max anyway. > > Also, it's IMHO better to do it in a seperate patch (series) after the > SCT Write Same support has entered libata's repo too, because this has > nothing to with it but TRIM translation. In case the future ACS > standards has clearer/better instruction on this, it will be easier > for us to revert/follow up too. > > And you'll need to fix the Block Limits VPD simulation > (ata_scsiop_inq_b0) too, so that it will advertise the Maximum Write > Same Length dynamically as per the logical sector size, otherwise your > effort will be completely in vain, even if our block layer is > overhauled in the future. > > Please be noted that, since your haven't touched ata_scsiop_inq_b0 at > all, the reported Maximum Write Same Length will be: > > On device with TRIM support: > - 4194240 LOGICAL sector per request split / command > -- ~=2G on non-4Kn drives > -- ~=16G on non-4Kn drives > > On device without TRIM support: > - 0 --> SD_MAX_WS10_BLOCKS (65535) per request split / command > -- ~= 32M on non-4Kn drives > -- ~=256M on non-4Kn drives > > Even if we ignore the upper limit(s) of the block layer, do we want > such inconsistencies? > -- 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
