Re: [PATCH 0/3] em28xx: add support for two buses on em2874 and upper

[Mauro Carvalho Chehab <mchehab@redhat.com>]

Em Tue, 5 Mar 2013 10:43:10 -0500
Devin Heitmueller <dheitmueller@kernellabs.com> escreveu:

> 2013/3/5 Mauro Carvalho Chehab <mchehab@redhat.com>:
> > The em2874 chips and upper have 2 buses. On all known devices, bus 0 is
> > currently used only by eeprom, and bus 1 for the rest. Add support to
> > register both buses.
> 
> Did you add a mutex to ensure that both buses cannot be used at the
> same time?  Because using the bus requires you to toggle a register
> (thus you cannot be using both busses at the same time), you cannot
> rely on the existing i2c adapter lock anymore.
> 
> You don't want a situation where something is actively talking on bus
> 0, and then something else tries to talk on bus 1, flips the register
> bit and then the thread talking on bus 0 starts failing.

Good point. The I2C mutex won't solve for this case. I'll add a mutex
there at the xfer function on a separate patch.

Cheers,
Mauro