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225785aec7
This patch reworks the way f_mass_storage.c handles memory barriers and synchronization: The driver now uses a wait_queue instead of doing its own task-state manipulations (even though only one task will ever use the wait_queue). The thread_wakeup_needed variable is removed. It was only a source of trouble; although it was what the driver tested to see whether it should wake up, what we really wanted to see was whether a USB transfer had completed. All the explicit memory barriers scattered throughout the driver are replaced by a few calls to smp_load_acquire() and smp_store_release(). The inreq_busy and outreq_busy fields are removed. In their place, the driver keeps track of the current I/O direction by splitting BUF_STATE_BUSY into two states: BUF_STATE_SENDING and BUF_STATE_RECEIVING. The buffer states are no longer protected by a lock. Mutual exclusion isn't needed; the state is changed only by the driver's main thread when it owns the buffer, and only by the request completion routine when the gadget core owns the buffer. The do_write() and throw_away_data() routines were reorganized to make efficient use of the new sleeping mechanism. This resulted in the removal of one indentation level in those routines, making the patch appear to be more more complicated than it really is. In a few places, the driver allowed itself to be frozen although it really shouldn't have (in the middle of executing a SCSI command). Those places have been fixed. The logic in the exception handler for aborting transfers and waiting for them to stop has been simplified. Tested-by: Thinh Nguyen <thinhn@synopsys.com> Signed-off-by: Alan Stern <stern@rowland.harvard.edu> Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com> |
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| atm | ||
| c67x00 | ||
| chipidea | ||
| class | ||
| common | ||
| core | ||
| dwc2 | ||
| dwc3 | ||
| early | ||
| gadget | ||
| host | ||
| image | ||
| isp1760 | ||
| misc | ||
| mon | ||
| mtu3 | ||
| musb | ||
| phy | ||
| renesas_usbhs | ||
| serial | ||
| storage | ||
| typec | ||
| usbip | ||
| wusbcore | ||
| Kconfig | ||
| Makefile | ||
| README | ||
| usb-skeleton.c | ||
To understand all the Linux-USB framework, you'll use these resources:
* This source code. This is necessarily an evolving work, and
includes kerneldoc that should help you get a current overview.
("make pdfdocs", and then look at "usb.pdf" for host side and
"gadget.pdf" for peripheral side.) Also, Documentation/usb has
more information.
* The USB 2.0 specification (from www.usb.org), with supplements
such as those for USB OTG and the various device classes.
The USB specification has a good overview chapter, and USB
peripherals conform to the widely known "Chapter 9".
* Chip specifications for USB controllers. Examples include
host controllers (on PCs, servers, and more); peripheral
controllers (in devices with Linux firmware, like printers or
cell phones); and hard-wired peripherals like Ethernet adapters.
* Specifications for other protocols implemented by USB peripheral
functions. Some are vendor-specific; others are vendor-neutral
but just standardized outside of the www.usb.org team.
Here is a list of what each subdirectory here is, and what is contained in
them.
core/ - This is for the core USB host code, including the
usbfs files and the hub class driver ("hub_wq").
host/ - This is for USB host controller drivers. This
includes UHCI, OHCI, EHCI, and others that might
be used with more specialized "embedded" systems.
gadget/ - This is for USB peripheral controller drivers and
the various gadget drivers which talk to them.
Individual USB driver directories. A new driver should be added to the
first subdirectory in the list below that it fits into.
image/ - This is for still image drivers, like scanners or
digital cameras.
../input/ - This is for any driver that uses the input subsystem,
like keyboard, mice, touchscreens, tablets, etc.
../media/ - This is for multimedia drivers, like video cameras,
radios, and any other drivers that talk to the v4l
subsystem.
../net/ - This is for network drivers.
serial/ - This is for USB to serial drivers.
storage/ - This is for USB mass-storage drivers.
class/ - This is for all USB device drivers that do not fit
into any of the above categories, and work for a range
of USB Class specified devices.
misc/ - This is for all USB device drivers that do not fit
into any of the above categories.