This is a note to let you know that I've just added the patch titled
usb-storage: Add quirk to defeat Kindle's automatic unload
to my usb git tree which can be found at git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git in the usb-linus branch.
The patch will show up in the next release of the linux-next tree (usually sometime within the next 24 hours during the week.)
The patch will hopefully also be merged in Linus's tree for the next -rc kernel release.
If you have any questions about this process, please let me know.
From 546aa0e4ea6ed81b6c51baeebc4364542fa3f3a7 Mon Sep 17 00:00:00 2001
From: Alan Stern stern@rowland.harvard.edu Date: Wed, 17 Mar 2021 15:06:54 -0400 Subject: usb-storage: Add quirk to defeat Kindle's automatic unload
Matthias reports that the Amazon Kindle automatically removes its emulated media if it doesn't receive another SCSI command within about one second after a SYNCHRONIZE CACHE. It does so even when the host has sent a PREVENT MEDIUM REMOVAL command. The reason for this behavior isn't clear, although it's not hard to make some guesses.
At any rate, the results can be unexpected for anyone who tries to access the Kindle in an unusual fashion, and in theory they can lead to data loss (for example, if one file is closed and synchronized while other files are still in the middle of being written).
To avoid such problems, this patch creates a new usb-storage quirks flag telling the driver always to issue a REQUEST SENSE following a SYNCHRONIZE CACHE command, and adds an unusual_devs entry for the Kindle with the flag set. This is sufficient to prevent the Kindle from doing its automatic unload, without interfering with proper operation.
Another possible way to deal with this would be to increase the frequency of TEST UNIT READY polling that the kernel normally carries out for removable-media storage devices. However that would increase the overall load on the system and it is not as reliable, because the user can override the polling interval. Changing the driver's behavior is safer and has minimal overhead.
CC: stable@vger.kernel.org Reported-and-tested-by: Matthias Schwarzott zzam@gentoo.org Signed-off-by: Alan Stern stern@rowland.harvard.edu Link: https://lore.kernel.org/r/20210317190654.GA497856@rowland.harvard.edu Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/usb/storage/transport.c | 7 +++++++ drivers/usb/storage/unusual_devs.h | 12 ++++++++++++ include/linux/usb_usual.h | 2 ++ 3 files changed, 21 insertions(+)
diff --git a/drivers/usb/storage/transport.c b/drivers/usb/storage/transport.c index 5eb895b19c55..f4304ce69350 100644 --- a/drivers/usb/storage/transport.c +++ b/drivers/usb/storage/transport.c @@ -656,6 +656,13 @@ void usb_stor_invoke_transport(struct scsi_cmnd *srb, struct us_data *us) need_auto_sense = 1; }
+ /* Some devices (Kindle) require another command after SYNC CACHE */ + if ((us->fflags & US_FL_SENSE_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 diff --git a/drivers/usb/storage/unusual_devs.h b/drivers/usb/storage/unusual_devs.h index 5732e9691f08..efa972be2ee3 100644 --- a/drivers/usb/storage/unusual_devs.h +++ b/drivers/usb/storage/unusual_devs.h @@ -2211,6 +2211,18 @@ UNUSUAL_DEV( 0x1908, 0x3335, 0x0200, 0x0200, USB_SC_DEVICE, USB_PR_DEVICE, NULL, US_FL_NO_READ_DISC_INFO ),
+/* + * Reported by Matthias Schwarzott zzam@gentoo.org + * The Amazon Kindle treats SYNCHRONIZE CACHE as an indication that + * the host may be finished with it, and automatically ejects its + * emulated 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_SENSE_AFTER_SYNC ), + /* * Reported by Oliver Neukum oneukum@suse.com * This device morphes spontaneously into another device if the access diff --git a/include/linux/usb_usual.h b/include/linux/usb_usual.h index 6b03fdd69d27..712363c7a2e8 100644 --- a/include/linux/usb_usual.h +++ b/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(SENSE_AFTER_SYNC, 0x80000000) \ + /* Do REQUEST_SENSE after SYNCHRONIZE_CACHE */ \
#define US_FLAG(name, value) US_FL_##name = value , enum { US_DO_ALL_FLAGS };