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The BeagleBoard.org PocketBeagle has P1 and P2 headers [0] which expose many of the TI AM3358 SoC balls to stacking expansion boards called "capes", or to other external connections like jumper wires connected to a breadboard. Note: the AM3358 die is actually embedded inside of the OSD335x-SM System-in-Package (SiP) [1] but that is irrelevant to the gpio driver. Many of the P1 and P2 header pins can muxed to a GPIO line. The gpio-line-names describe which P1 or P2 pin that line goes to and the default mux for that P1 or P2 pin if it is not GPIO. Some GPIO lines are named "[NC]" as the corresponding balls are not routed to anything on the PCB. The goal for these names is to make it easier for a user viewing the output of gpioinfo to determine which P1 or P2 pin is connected to a GPIO line. The output of gpioinfo on a PocketBeagle would be: gpiochip0 - 32 lines: line 0: "[NC]" unused input active-high line 1: "[NC]" unused input active-high line 2: "P1.08 [SPI0_CLK]" unused input active-high line 3: "P1.10 [SPI0_MISO]" unused input active-high line 4: "P1.12 [SPI0_MOSI]" unused input active-high line 5: "P1.06 [SPI0_CS]" unused input active-high line 6: "[MMC0_CD]" "cd" input active-low [used] line 7: "P2.29 [SPI1_CLK]" unused input active-high line 8: "[SYSBOOT]" unused input active-high line 9: "[SYSBOOT]" unused input active-high line 10: "[SYSBOOT]" unused input active-high line 11: "[SYSBOOT]" unused input active-high line 12: "P1.26 [I2C2_SDA]" unused input active-high line 13: "P1.28 [I2C2_SCL]" unused input active-high line 14: "P2.11 [I2C1_SDA]" unused input active-high line 15: "P2.09 [I2C1_SCL]" unused input active-high line 16: "[NC]" unused input active-high line 17: "[NC]" unused input active-high line 18: "[NC]" unused input active-high line 19: "P2.31 [SPI1_CS]" unused input active-high line 20: "P1.20 [PRU0.16]" unused input active-high line 21: "[NC]" unused input active-high line 22: "[NC]" unused input active-high line 23: "P2.03" unused input active-high line 24: "[NC]" unused input active-high line 25: "[NC]" unused input active-high line 26: "P1.34" unused input active-high line 27: "P2.19" unused input active-high line 28: "[NC]" unused input active-high line 29: "[NC]" unused input active-high line 30: "P2.05 [UART4_RX]" unused input active-high line 31: "P2.07 [UART4_TX]" unused input active-high gpiochip1 - 32 lines: line 0: "[NC]" unused input active-high line 1: "[NC]" unused input active-high line 2: "[NC]" unused input active-high line 3: "[NC]" unused input active-high line 4: "[NC]" unused input active-high line 5: "[NC]" unused input active-high line 6: "[NC]" unused input active-high line 7: "[NC]" unused input active-high line 8: "[NC]" unused input active-high line 9: "P2.25 [SPI1_MOSI]" unused input active-high line 10: "P1.32 [UART0_RX]" unused input active-high line 11: "P1.30 [UART0_TX]" unused input active-high line 12: "P2.24" unused input active-high line 13: "P2.33" unused input active-high line 14: "P2.22" unused input active-high line 15: "P2.18" unused input active-high line 16: "[NC]" unused input active-high line 17: "[NC]" unused input active-high line 18: "P2.01 [PWM1A]" unused input active-high line 19: "[NC]" unused input active-high line 20: "P2.10" unused input active-high line 21: "[USR LED 0]" "beaglebone:green:usr0" output active-high [used] line 22: "[USR LED 1]" "beaglebone:green:usr1" output active-high [used] line 23: "[USR LED 2]" "beaglebone:green:usr2" output active-high [used] line 24: "[USR LED 3]" "beaglebone:green:usr3" output active-high [used] line 25: "P2.06" unused input active-high line 26: "P2.04" unused input active-high line 27: "P2.02" unused input active-high line 28: "P2.08" unused input active-high line 29: "[NC]" unused input active-high line 30: "[NC]" unused input active-high line 31: "[NC]" unused input active-high gpiochip2 - 32 lines: line 0: "P2.20" unused input active-high line 1: "P2.17" unused input active-high line 2: "[NC]" unused input active-high line 3: "[NC]" unused input active-high line 4: "[NC]" unused input active-high line 5: "[EEPROM_WP]" unused input active-high line 6: "[SYSBOOT]" unused input active-high line 7: "[SYSBOOT]" unused input active-high line 8: "[SYSBOOT]" unused input active-high line 9: "[SYSBOOT]" unused input active-high line 10: "[SYSBOOT]" unused input active-high line 11: "[SYSBOOT]" unused input active-high line 12: "[SYSBOOT]" unused input active-high line 13: "[SYSBOOT]" unused input active-high line 14: "[SYSBOOT]" unused input active-high line 15: "[SYSBOOT]" unused input active-high line 16: "[SYSBOOT]" unused input active-high line 17: "[SYSBOOT]" unused input active-high line 18: "[NC]" unused input active-high line 19: "[NC]" unused input active-high line 20: "[NC]" unused input active-high line 21: "[NC]" unused input active-high line 22: "P2.35 [AIN5]" unused input active-high line 23: "P1.02 [AIN6]" unused input active-high line 24: "P1.35 [PRU1.10]" unused input active-high line 25: "P1.04 [PRU1.11]" unused input active-high line 26: "[MMC0_DAT3]" unused input active-high line 27: "[MMC0_DAT2]" unused input active-high line 28: "[MMC0_DAT1]" unused input active-high line 29: "[MMC0_DAT0]" unused input active-high line 30: "[MMC0_CLK]" unused input active-high line 31: "[MMC0_CMD]" unused input active-high gpiochip3 - 32 lines: line 0: "[NC]" unused input active-high line 1: "[NC]" unused input active-high line 2: "[NC]" unused input active-high line 3: "[NC]" unused input active-high line 4: "[NC]" unused input active-high line 5: "[I2C0_SDA]" unused input active-high line 6: "[I2C0_SCL]" unused input active-high line 7: "[JTAG]" unused input active-high line 8: "[JTAG]" unused input active-high line 9: "[NC]" unused input active-high line 10: "[NC]" unused input active-high line 11: "[NC]" unused input active-high line 12: "[NC]" unused input active-high line 13: "P1.03 [USB1]" unused input active-high line 14: "P1.36 [PWM0A]" unused input active-high line 15: "P1.33 [PRU0.1]" unused input active-high line 16: "P2.32 [PRU0.2]" unused input active-high line 17: "P2.30 [PRU0.3]" unused input active-high line 18: "P1.31 [PRU0.4]" unused input active-high line 19: "P2.34 [PRU0.5]" unused input active-high line 20: "P2.28 [PRU0.6]" unused input active-high line 21: "P1.29 [PRU0.7]" unused input active-high line 22: "[NC]" unused input active-high line 23: "[NC]" unused input active-high line 24: "[NC]" unused input active-high line 25: "[NC]" unused input active-high line 26: "[NC]" unused input active-high line 27: "[NC]" unused input active-high line 28: "[NC]" unused input active-high line 29: "[NC]" unused input active-high line 30: "[NC]" unused input active-high line 31: "[NC]" unused input active-high [0] https://github.com/beagleboard/pocketbeagle/wiki/System-Reference-Manual#71_Expansion_Header_Connectors [1] https://octavosystems.com/app_notes/osd335x-family-pin-assignments/ Reviewed-by: Jason Kridner <jason@beagleboard.org> Reviewed-by: Robert Nelson <robertcnelson@gmail.com> Signed-off-by: Drew Fustini <drew@beagleboard.org> Signed-off-by: Tony Lindgren <tony@atomide.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.