On Tue, Mar 16, 2021 at 06:26:30AM +0100, Matthias Schwarzott wrote: > I implemented solution 3b. This is the pullrequest for udev (systemd > repository): > > https://github.com/systemd/systemd/pull/19002 > > Now Lennart asks if udev is the best place for such hacks/work-arounds? > > Well, I implemented it as suggested by Alan (see above). This was the > simplest of the considered alternatives. Different quirks in kernel has been > considered, but are more effort to be implemented. Lennart probably isn't aware how the usb-storage driver works. It does not create commands on its own; it merely sends the commands that it gets from higher SCSI layers. It may be possible to modify the SCSI core, to make it send a TEST UNIT READY command immediately following any SYNCHRONIZE CACHE to a Kindle. However, there may be an easier solution. usb-storage does indeed send a command of its own, REQUEST SENSE, to get error data when a command fails. The patch below will make it do the same thing whenever it sends a SYNCHRONIZE CACHE to a Kindle, failure or not. The only question is whether the Kindle will regard REQUEST SENSE as a sufficient indication that it shouldn't do an eject. The only way to find out is by testing the patch. Alan Stern Index: usb-devel/drivers/usb/storage/transport.c =================================================================== --- usb-devel.orig/drivers/usb/storage/transport.c +++ usb-devel/drivers/usb/storage/transport.c @@ -656,6 +656,13 @@ void usb_stor_invoke_transport(struct sc need_auto_sense = 1; } + /* Some devices (Kindle) require another command after SYNC CACHE */ + if (us->fflags & US_FL_CHECK_AFTER_SYNC && + srb->cmnd[0] == SYNCHRONIZE_CACHE) { + usb_stor_dbg(us, "-- sense after SYNC CACHE\n"); + need_auto_sense = 1; + } + /* * If we have a failure, we're going to do a REQUEST_SENSE * automatically. Note that we differentiate between a command Index: usb-devel/drivers/usb/storage/unusual_devs.h =================================================================== --- usb-devel.orig/drivers/usb/storage/unusual_devs.h +++ usb-devel/drivers/usb/storage/unusual_devs.h @@ -2212,6 +2212,18 @@ UNUSUAL_DEV( 0x1908, 0x3335, 0x0200, 0x0 US_FL_NO_READ_DISC_INFO ), /* + * Reported by Matthias Schwarzott <zzam@xxxxxxxxxx> + * The Amazon Kindle treats SYNCHRONIZE CACHE as an indication that + * the host may be finished with it, and automatically ejects its + * media unless it receives another command within one second. + */ +UNUSUAL_DEV( 0x1949, 0x0004, 0x0000, 0x9999, + "Amazon", + "Kindle", + USB_SC_DEVICE, USB_PR_DEVICE, NULL, + US_FL_CHECK_AFTER_SYNC ), + +/* * Reported by Oliver Neukum <oneukum@xxxxxxxx> * This device morphes spontaneously into another device if the access * pattern of Windows isn't followed. Thus writable media would be dirty Index: usb-devel/include/linux/usb_usual.h =================================================================== --- usb-devel.orig/include/linux/usb_usual.h +++ usb-devel/include/linux/usb_usual.h @@ -86,6 +86,8 @@ /* lies about caching, so always sync */ \ US_FLAG(NO_SAME, 0x40000000) \ /* Cannot handle WRITE_SAME */ \ + US_FLAG(CHECK_AFTER_SYNC, 0x80000000) \ + /* Check sense after SYNCHRONIZE_CACHE */ \ #define US_FLAG(name, value) US_FL_##name = value , enum { US_DO_ALL_FLAGS };
