diff options
| author | Maxim Devaev <mdevaev@gmail.com> | 2022-07-11 13:29:57 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2022-07-14 16:06:42 +0200 |
| commit | 421c8d9a20da92deed2dac227e7ebdee7eb3e88f (patch) | |
| tree | 9dd7b02019b4500836d798ac73042c36735cfe6f /Documentation/usb | |
| parent | 8097cf2fb3b2205257f1c76f4808e3398d66b6d9 (diff) | |
usb: gadget: f_mass_storage: forced_eject attribute
It allows to reset prevent_medium_removal flag and "eject" the image.
This can be useful to free the drive from a hunging host or if the host
continues to use the drive even after unmounting (Linux does this).
It's also a bit like using an unfolded paperclip on an optical drive.
Previously, the undocumented method of sending SIGUSR1 to a special
"file-storage" kernel thread could be used for these purposes,
but when using multiple storages there was no way to distinguish
one from the other, so we had to send a signal to everyone.
Reviewed-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Maxim Devaev <mdevaev@gmail.com>
Link: https://lore.kernel.org/r/20220711102956.19642-1-mdevaev@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'Documentation/usb')
| -rw-r--r-- | Documentation/usb/gadget-testing.rst | 6 | ||||
| -rw-r--r-- | Documentation/usb/mass-storage.rst | 9 |
2 files changed, 15 insertions, 0 deletions
diff --git a/Documentation/usb/gadget-testing.rst b/Documentation/usb/gadget-testing.rst index 1c37159fa171..2278c9ffb74a 100644 --- a/Documentation/usb/gadget-testing.rst +++ b/Documentation/usb/gadget-testing.rst @@ -333,6 +333,12 @@ In each lun directory there are the following attribute files: being a CD-ROM. nofua Flag specifying that FUA flag in SCSI WRITE(10,12) + forced_eject This write-only file is useful only when + the function is active. It causes the backing + file to be forcibly detached from the LUN, + regardless of whether the host has allowed it. + Any non-zero number of bytes written will + result in ejection. =============== ============================================== Testing the MASS STORAGE function diff --git a/Documentation/usb/mass-storage.rst b/Documentation/usb/mass-storage.rst index d181b47c3cb6..f399ec631599 100644 --- a/Documentation/usb/mass-storage.rst +++ b/Documentation/usb/mass-storage.rst @@ -181,6 +181,15 @@ sysfs entries Reflects the state of nofua flag for given logical unit. It can be read and written. + - forced_eject + + When written into, it causes the backing file to be forcibly + detached from the LUN, regardless of whether the host has allowed + it. The content doesn't matter, any non-zero number of bytes + written will result in ejection. + + Can not be read. + Other then those, as usual, the values of module parameters can be read from /sys/module/g_mass_storage/parameters/* files. |