It allows to reset prevent_medium_removal flag and "eject" the image. The patch is a completely alternative implementation of the previously proposed [1], the idea of which was born after the mentioned discussion. Reviewed-by: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> Signed-off-by: Maxim Devaev <mdevaev@xxxxxxxxx> Link: https://lore.kernel.org/lkml/20220406092445.215288-1-mdevaev@xxxxxxxxx [1] --- v3 -> v4: Added comment for fsg_store_forced_eject() internals v2 -> v3: Improved spelling v1 -> v2: Added documentation for the ABI and sysfs .../testing/configfs-usb-gadget-mass-storage | 6 +++++ Documentation/usb/gadget-testing.rst | 6 +++++ Documentation/usb/mass-storage.rst | 9 +++++++ drivers/usb/gadget/function/f_mass_storage.c | 25 +++++++++++++++++++ drivers/usb/gadget/function/storage_common.c | 15 +++++++++++ drivers/usb/gadget/function/storage_common.h | 2 ++ 6 files changed, 63 insertions(+) diff --git a/Documentation/ABI/testing/configfs-usb-gadget-mass-storage b/Documentation/ABI/testing/configfs-usb-gadget-mass-storage index c86b63a7bb43..d899adb57e81 100644 --- a/Documentation/ABI/testing/configfs-usb-gadget-mass-storage +++ b/Documentation/ABI/testing/configfs-usb-gadget-mass-storage @@ -32,4 +32,10 @@ Description: 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. =========== ============================================== diff --git a/Documentation/usb/gadget-testing.rst b/Documentation/usb/gadget-testing.rst index c18113077889..15624c4fe633 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. diff --git a/drivers/usb/gadget/function/f_mass_storage.c b/drivers/usb/gadget/function/f_mass_storage.c index 6ad669dde41c..00cac2a38178 100644 --- a/drivers/usb/gadget/function/f_mass_storage.c +++ b/drivers/usb/gadget/function/f_mass_storage.c @@ -2520,10 +2520,21 @@ static ssize_t file_store(struct device *dev, struct device_attribute *attr, return fsg_store_file(curlun, filesem, buf, count); } +static ssize_t forced_eject_store(struct device *dev, + struct device_attribute *attr, + const char *buf, size_t count) +{ + struct fsg_lun *curlun = fsg_lun_from_dev(dev); + struct rw_semaphore *filesem = dev_get_drvdata(dev); + + return fsg_store_forced_eject(curlun, filesem, buf, count); +} + static DEVICE_ATTR_RW(nofua); /* mode wil be set in fsg_lun_attr_is_visible() */ static DEVICE_ATTR(ro, 0, ro_show, ro_store); static DEVICE_ATTR(file, 0, file_show, file_store); +static DEVICE_ATTR_WO(forced_eject); /****************************** FSG COMMON ******************************/ @@ -2677,6 +2688,7 @@ static struct attribute *fsg_lun_dev_attrs[] = { &dev_attr_ro.attr, &dev_attr_file.attr, &dev_attr_nofua.attr, + &dev_attr_forced_eject.attr, NULL }; @@ -3090,6 +3102,18 @@ static ssize_t fsg_lun_opts_inquiry_string_store(struct config_item *item, CONFIGFS_ATTR(fsg_lun_opts_, inquiry_string); +static ssize_t fsg_lun_opts_forced_eject_store(struct config_item *item, + const char *page, size_t len) +{ + struct fsg_lun_opts *opts = to_fsg_lun_opts(item); + struct fsg_opts *fsg_opts = to_fsg_opts(opts->group.cg_item.ci_parent); + + return fsg_store_forced_eject(opts->lun, &fsg_opts->common->filesem, + page, len); +} + +CONFIGFS_ATTR_WO(fsg_lun_opts_, forced_eject); + static struct configfs_attribute *fsg_lun_attrs[] = { &fsg_lun_opts_attr_file, &fsg_lun_opts_attr_ro, @@ -3097,6 +3121,7 @@ static struct configfs_attribute *fsg_lun_attrs[] = { &fsg_lun_opts_attr_cdrom, &fsg_lun_opts_attr_nofua, &fsg_lun_opts_attr_inquiry_string, + &fsg_lun_opts_attr_forced_eject, NULL, }; diff --git a/drivers/usb/gadget/function/storage_common.c b/drivers/usb/gadget/function/storage_common.c index b859a158a414..03035dbbe97b 100644 --- a/drivers/usb/gadget/function/storage_common.c +++ b/drivers/usb/gadget/function/storage_common.c @@ -519,4 +519,19 @@ ssize_t fsg_store_inquiry_string(struct fsg_lun *curlun, const char *buf, } EXPORT_SYMBOL_GPL(fsg_store_inquiry_string); +ssize_t fsg_store_forced_eject(struct fsg_lun *curlun, struct rw_semaphore *filesem, + const char *buf, size_t count) +{ + int ret; + + /* + * Forcibly detach the backing file from the LUN + * regardless of whether the host has allowed it. + */ + curlun->prevent_medium_removal = 0; + ret = fsg_store_file(curlun, filesem, "", 0); + return ret < 0 ? ret : count; +} +EXPORT_SYMBOL_GPL(fsg_store_forced_eject); + MODULE_LICENSE("GPL"); diff --git a/drivers/usb/gadget/function/storage_common.h b/drivers/usb/gadget/function/storage_common.h index bdeb1e233fc9..0a544a82cbf8 100644 --- a/drivers/usb/gadget/function/storage_common.h +++ b/drivers/usb/gadget/function/storage_common.h @@ -219,5 +219,7 @@ ssize_t fsg_store_removable(struct fsg_lun *curlun, const char *buf, size_t count); ssize_t fsg_store_inquiry_string(struct fsg_lun *curlun, const char *buf, size_t count); +ssize_t fsg_store_forced_eject(struct fsg_lun *curlun, struct rw_semaphore *filesem, + const char *buf, size_t count); #endif /* USB_STORAGE_COMMON_H */ -- 2.37.0
