Writing into user memory

[jivedingo]

I'm writing a custom serial port char driver, and I'm still not quite sure how to implement one of the extra features I need.

The driver has to be able to read a certain amount of bytes from the serial port and store them in a file in user-space memory. This must be done on an interrupt routine, and not requested by a user process. The device then functions as a normal char driver, and lets user processes access it through a device. I can think of several hacky ways that this could probably be done, but I think I'm probably missing out on a standard procedure that would be the most efficient way.

Does anyone have any suggestions on the best way to implement the write to user-space memory? I can figure out the rest easily enough myself (ie. the hardware control, driver states, interrupts, etc.)

[jivedingo]

alternatively - Is there a way that my driver could just alert a perpetually-running user process to handle the read, and only allow access to that process for the first little while?
Would this be better or worse...?

[matt_kleviar]

how about copy_from_user and copy_to_user function use ?!!

[ndevel]

...never use copy_from_user and copy_to_user in interrupt context

[matt_kleviar]

yeah, because can it sleep ! we do not use it in the inteupt handler but we can use it in driver, isnt it ?

[ndevel]

... approved

[matt_kleviar]

Hi ndlevel,
can you please reply to the thread created by me named "kernel address space" ?
if possible.

[Jeffrey.Cao]

Use softirq/tasklet, and in the bottom half, do the copy_to_user.

[matt_kleviar]

and how about get_user_pages !! ?