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diff --git a/README.md b/README.md new file mode 100644 index 0000000..331f52c --- /dev/null +++ b/README.md @@ -0,0 +1,39 @@ +memtool +======= + +memtool is a program that allows to access memory mapped registers. This is +useful to inspect and modify registers from the command line. + +By default memtool uses `/dev/mem` to operate. So to actually work you need to +have `DEVMEM` enabled in the kernel. Note that depending on further kernel +configuration you can only access unused io-memory, see the kernel +configuration knobs `IO_STRICT_DEVMEM` and `STRICT_DEVMEM`. Also note that +there might be further restrictions. E.g. on several i.MX ARM SoCs register +access is not possible from user mode for certain areas unless configured +otherwise. + +memtool can also operate on plain files, and access PHY registers (via the +`ioctl`s `SIOCSMIIREG` and `SIOCGMIIREG`). + +Examples +--------- + + * Write a 32-bit wide 0 to register at address 0x73f00040 + + ```sh + # memtool mw -l 0x73f00040 0 + ``` + + * Read the first two registers of the default PHY attached to network device + `eth0`: + + ```sh + # memtool md -s mdio:eth0. -w 0+4 + ``` + + * Place a (usually red) dot on the framebuffer: + + ```sh + # memtool mw -d /dev/fb0 -w 0 0xfc00 + ``` + |