CODEWITHSUNDEEP
linuxu-boot
manstud
manstud

Reputation: 39

what does "usb start" command do exactly?

I am facing a problem when i try to read from usb device at u-boot.

When i do 

      fatls usb 0:1

it says bad device. But as soon as i do 

      usb start
      fatls usb 0:1

then it shows me correcly the fat partition in USB.

I was looking to add both commands in the common/main.c so that whenever the board boots it looks for the fat partition of USB.

It is tough but i need to do it.

Anybody has a clue??

Upvotes: 0

Views: 2836

Answers (1)

Tom Rini
Tom Rini

Reputation: 2173

As has been said in the comments, "usb start" is what initializes the USB subsystem and scans attached devices for things U-Boot can deal with (USB sticks, ethernet, etc). Unlike some buses such as MMC that we will do an initial scan on prior to starting the shell, for USB you must run the start command first if you expect to use devices that are attached.

Now, you don't add things to common/main.c, you add things to the bootcmd environment variable (and this can be changed in the boards config.h file so that the default environment is changed, if you are working on a board where you cannot do 'saveenv' to save your changes in a persistent way). So what you would want to do is:

=> setenv bootcmd 'usb start;fatls usb 0:1'

or whatever commands you wish to do with the files present on the USB stick.

Upvotes: 1

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