Re: How to assess PMP register

[s ticket <smticket@gmail.com>]

2009/5/6 Gwendal Grignou <gwendal@google.com>:
> - you can not access a PMP device from user space directly because
> there is no file descriptor for it.
> - however, libata stores a dump of PMP registers taken after every
> reset in gscr structure of the ata_device structure that represent the
> PMP in the kernel. You can modify libata to print the registers you
> need.

I add a  `pmp_attach' function ata_port_operation, and call
`sata_pmp_read' in that
function. It works fine. But when I call `sata_pmp_read' in process
context while another
process is writing to disks, the kernel hangs (deadlock?). Is there
any suggestion?
I found that `sata_pmp_read' finally calls `ata_exec_internal_sg' to
do the real work and
'ata_exec_internal_sg' takes ata_port->lock.

BTW, why `sata_pmp_read' and `sata_pmp_write' aren't exported?


                                                jbin