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From Stephen Warren: ARM: tegra: USB driver cleanup The Tegra USB driver has a number of issues: 1) The PHY driver isn't a true platform device, and doesn't implement the standard USB PHY API. 2) struct device instance numbers were used to make decisions in the driver, rather than being parameterized by DT or platform data. This pull request solves issue (2), and lays the groundwork for solving issue (1). The work on issue (1) involved introducing new DT nodes for the USB PHYs, which in turn interacted with the Tegra common clock framework changes, due to the move of clock lookups into device tree. Hence, these USB driver changes are taken through the Tegra tree with acks from USB maintainers. This pull request is based on the previous pull request, with tag tegra-for-3.9-soc-ccf. * tag 'tegra-for-3.9-soc-usb' of git://git.kernel.org/pub/scm/linux/kernel/git/swarren/linux-tegra: usb: host: tegra: make use of PHY pointer of HCD ARM: tegra: Add reset GPIO information to PHY DT node usb: host: tegra: don't touch EMC clock usb: add APIs to access host registers from Tegra PHY USB: PHY: tegra: Get rid of instance number to differentiate PHY type USB: PHY: tegra: get rid of instance number to differentiate legacy controller ARM: tegra: add clocks properties to USB PHY nodes ARM: tegra: add DT nodes for Tegra USB PHY usb: phy: remove unused APIs from Tegra PHY. usb: host: tegra: Resetting PORT0 based on information received via DT. ARM: tegra: Add new DT property to USB node. usb: phy: use kzalloc to allocate struct tegra_usb_phy ARM: tegra: remove USB address related macros from iomap.h
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 ("khubd").
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.