[PATCH 1/3] misc: Add Aspeed BT IPMI host driver

On 09/12/2016 04:23 PM, C?dric Le Goater wrote:

Hello,

On 09/12/2016 10:33 PM, Corey Minyard wrote:

quoted

On 09/12/2016 02:15 PM, Arnd Bergmann wrote:

quoted

On Monday, September 12, 2016 1:55:40 PM CEST Corey Minyard wrote:

quoted

On 09/02/2016 08:22 AM, C?dric Le Goater wrote:

quoted

Hello,

Adding Corey in cc: . I guess I should have done that in the first place.

Yes, probably so.  I've been travelling and didn't see it on the mailing
lists until now.

There is already a BT driver in the kernel, in drivers/char/ipmi, why
won't that work?

The new driver is the host side (running on the BMC), the existing one
is the client (running on the PC).

     Arnd

Ok, that's not really clear from the documentation or the Kconfig.
In the IPMI spec the "host" side is the computer side, not the BMC
side.  Like:

    11.6.1 BT Host Interface Registers
    The Host BT interface provides an independent set of registers and
    interrupts to allow the Host driver to
    communicate with the baseboard management controller without
    conflicting with the O/S ACPI driver.

In light of that, this should probably be named the bt-bmc driver.

I haven't reviewed this in detail, but I'm ok with putting it in
drivers/char/ipmi.  The state machine part looks reasonably
generic.  The configuration part isn't, but that could be split
out later if necessary.

The biggest thing I don't like is the byte at a time interfaces
from userspace.  That seems fairly inefficient if the system
does extra work for each userspace access.  IIRC some
systems do and some don't.

What about the ioctl to send an SMS ATN event to the host ? Is
that ok for you ?

Yeah, that's necessary, there's no way the low-level driver can
know when to do that.

I have a similar piece of code in the qemu IPMI emulator, even
the external IPMI emulator has a message it sends to set ATTN.

I did look at similarities between the two pieces of code, but
the qemu one has to be register-read/write driven, so it's
completely different in design.

-corey

Thanks,

C.