Dear Simon,
In message 20210919185950.3813952-3-sjg@chromium.org you wrote:
Move this from the README to rST format.
Just a few nitpicks...
diff --git a/doc/usage/environment.rst b/doc/usage/environment.rst new file mode 100644 index 00000000000..be785a8f717 --- /dev/null +++ b/doc/usage/environment.rst @@ -0,0 +1,382 @@ +.. SPDX-License-Identifier: GPL-2.0+
+Environment Variables +=====================
+U-Boot supports user configuration using Environment Variables which +can be made persistent by saving to Flash memory.
...by saving to persistent storage, for example flash memory.
+Environment Variables are set using "setenv", printed using +"printenv", and saved to Flash using "saveenv". Using "setenv"
Environment Variables are set using "env set" (alias "setenv"), printed using "env print" (alias "printenv"), and saved to persistent storage using "env save" (alias "saveenv"). Using "env set" ...
+Some configuration options can be set using Environment Variables.
This probably needs an explanation what "configuration options' means here?
+Image locations +---------------
+The following image location variables contain the location of images +used in booting. The "Image" column gives the role of the image and is +not an environment variable name. The other columns are environment +variable names. "File Name" gives the name of the file on a TFTP +server, "RAM Address" gives the location in RAM the image will be +loaded to, and "Flash Location" gives the image's address in NOR +flash or offset in NAND flash.
+*Note* - these variables don't have to be defined for all boards, some +boards currently use other variables for these purposes, and some +boards use these variables for other purposes.
+================= ============== ================ ============== +Image File Name RAM Address Flash Location +================= ============== ================ ============== +u-boot u-boot u-boot_addr_r u-boot_addr +Linux kernel bootfile kernel_addr_r kernel_addr +device tree blob fdtfile fdt_addr_r fdt_addr +ramdisk ramdiskfile ramdisk_addr_r ramdisk_addr +================= ============== ================ ==============
Maybe it should be pointed out that this is just a commonly used set of variable names, used in some other variable definitions, but is in no way hard coded anywhere in U-Boot code.
OK, I see that "bootfile" and ""fdtfile" are now actually used in some code - but IMO this is a bad idea and should be fixed.
+Automatically updated variables +-------------------------------
+The following environment variables may be used and automatically +updated by the network boot commands ("bootp" and "rarpboot"), +depending the information provided by your boot server:
+========= =================================================== +Variable Notes +========= =================================================== +bootfile see above +dnsip IP address of your Domain Name Server +dnsip2 IP address of your secondary Domain Name Server +gatewayip IP address of the Gateway (Router) to use +hostname Target hostname +ipaddr See above +netmask Subnet Mask +rootpath Pathname of the root filesystem on the NFS server +serverip see above +========= ===================================================
This list is incomplete; for example, sysboot sets bootfile, too.
For completeness, .flags etc. should be documented, too [but yes, this is a separate task of course].
Best regards,
Wolfgang Denk