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Diffstat (limited to 'doc/driver-model/UDM-serial.txt')
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diff --git a/doc/driver-model/UDM-serial.txt b/doc/driver-model/UDM-serial.txt deleted file mode 100644 index ed804a8e7e..0000000000 --- a/doc/driver-model/UDM-serial.txt +++ /dev/null @@ -1,155 +0,0 @@ -The U-Boot Driver Model Project -=============================== -Serial I/O analysis -=================== -Marek Vasut <marek.vasut@gmail.com> -2012-02-20 - -I) Overview ------------ - -The serial port support currently requires the driver to export the following -functions: - - serial_putc() ...... Output a character - serial_puts() ...... Output string, often done using serial_putc() - serial_tstc() ...... Test if incoming character is in a buffer - serial_getc() ...... Retrieve incoming character - serial_setbrg() .... Configure port options - serial_init() ...... Initialize the hardware - -The simpliest implementation, supporting only one port, simply defines these six -functions and calls them. Such calls are scattered all around U-Boot, especiall -serial_putc(), serial_puts(), serial_tstc() and serial_getc(). The serial_init() -and serial_setbrg() are often called from platform-dependent places. - -It's important to consider current implementation of CONFIG_SERIAL_MULTI though. -This resides in common/serial.c and behaves as a multiplexer for serial ports. -This, by calling serial_assign(), allows user to switch I/O from one serial port -to another. Though the environmental variables "stdin", "stdout", "stderr" -remain set to "serial". - -These variables are managed by the IOMUX. This resides in common/iomux.c and -manages all console input/output from U-Boot. For serial port, only one IOMUX is -always registered, called "serial" and the switching of different serial ports -is done by code in common/serial.c. - -On a final note, it's important to mention function default_serial_console(), -which is platform specific and reports the default serial console for the -platform, unless proper environment variable overrides this. - -II) Approach ------------- - -Drivers not using CONFIG_SERIAL_MULTI already will have to be converted to -similar approach. The probe() function of a driver will call a function -registering the driver with a STDIO subsystem core, stdio_device_register(). - -The serial_init() function will now be replaced by probe() function of the -driver, the rest of the components of the driver will be converted to standard -STDIO driver calls. See [ UDM-stdio.txt ] for details. - -The serial_setbrg() function depends on global data pointer. This is wrong, -since there is likely to be user willing to configure different baudrate on two -different serial ports. The function will be replaced with STDIO's "conf()" -call, with STDIO_CONFIG_SERIAL_BAUDRATE argument. - -III) Analysis of in-tree drivers --------------------------------- - - altera_jtag_uart.c - ------------------ - No support for CONFIG_SERIAL_MULTI. Simple conversion possible. - - altera_uart.c - ------------- - No support for CONFIG_SERIAL_MULTI. Simple conversion possible. - - arm_dcc.c - --------- - No support for CONFIG_SERIAL_MULTI. Simple conversion possible, unless used - with CONFIG_ARM_DCC_MULTI. Then it registers another separate IOMUX. - - atmel_usart.c - ------------- - No support for CONFIG_SERIAL_MULTI. Simple conversion possible. - - mcfuart.c - --------- - No support for CONFIG_SERIAL_MULTI. Simple conversion possible. - - ns16550.c - --------- - This driver seems complicated and certain consideration will need to be made - during conversion. This driver is implemented in very universal manner, - therefore it'll be necessary to properly design it's platform_data. - - opencores_yanu.c - ---------------- - No support for CONFIG_SERIAL_MULTI. Simple conversion possible. - - sandbox.c - --------- - No support for CONFIG_SERIAL_MULTI. Simple conversion possible. - - serial.c - -------- - This is a complementary part of NS16550 UART driver, see above. - - serial_imx.c - ------------ - No support for CONFIG_SERIAL_MULTI. Simple conversion possible. This driver - might be removed in favor of serial_mxc.c . - - serial_ks8695.c - --------------- - No support for CONFIG_SERIAL_MULTI. Simple conversion possible. - - serial_max3100.c - ---------------- - No support for CONFIG_SERIAL_MULTI. Simple conversion possible. - - serial_mxc.c - ------------ - No support for CONFIG_SERIAL_MULTI. Simple conversion possible. - - serial_pl01x.c - -------------- - No support for CONFIG_SERIAL_MULTI. Simple conversion possible, though this - driver in fact contains two drivers in total. - - serial_pxa.c - ------------ - This driver is a bit complicated, but due to clean support for - CONFIG_SERIAL_MULTI, there are no expected obstructions throughout the - conversion process. - - serial_s3c24x0.c - ---------------- - This driver, being quite ad-hoc might need some work to bring back to shape. - - serial_s5p.c - ------------ - No support for CONFIG_SERIAL_MULTI. Simple conversion possible. - - serial_sa1100.c - --------------- - No support for CONFIG_SERIAL_MULTI. Simple conversion possible. - - serial_sh.c - ----------- - No support for CONFIG_SERIAL_MULTI. Simple conversion possible. - - serial_xuartlite.c - ------------------ - No support for CONFIG_SERIAL_MULTI. Simple conversion possible. - - usbtty.c - -------- - This driver seems very complicated and entangled with USB framework. The - conversion might be complicated here. - - arch/powerpc/cpu/mpc512x/serial.c - --------------------------------- - This driver supports CONFIG_SERIAL_MULTI. This driver will need to be moved to - proper place. |