usb: gadget: f_mass_storage: forced_eject attribute
Subsystems (2)
PATCH v5 1/1 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 <[email protected]>
Signed-off-by Maxim Devaev <[email protected]>
---
v4 -> v5: A more detailed description of the commit 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(+)
Documentation/ABI/testing/configfs-usb-gadget-mass-storage +6 -0
@@ -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. =========== ==============================================
Documentation/usb/gadget-testing.rst +6 -0
@@ -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
Documentation/usb/mass-storage.rst +9 -0
@@ -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.
drivers/usb/gadget/function/f_mass_storage.c +25 -0
@@ -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, };
drivers/usb/gadget/function/storage_common.c +15 -0
@@ -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" );
drivers/usb/gadget/function/storage_common.h +2 -0
@@ -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 */
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2.37.0