On Tue, Aug 21, 2012 at 04:28:20PM -0700, Shirish S wrote: > On Tue, Aug 21, 2012 at 7:56 AM, Ville Syrjälä < > ville.syrjala@xxxxxxxxxxxxxxx> wrote: > > > On Tue, Aug 21, 2012 at 06:55:53AM -0700, Shirish S wrote: > Here are my earlier comments on Jean's patch: > > http://lists.freedesktop.org/archives/dri-devel/2012-February/019069.html > > > > > If i am not wrong am doing exactly what you have said in you comments. > > This seems a bit wrong to me. The spec says that the ack for the > segment address is "don't care", but for the segment pointer the ack is > required (when segment != 0). > The variable segFlags is "dont care for block 0 and 1 wheras". > > With I2C_M_IGNORE_NAK we would in fact end up reading segment 0 from a > non E-DDC display, if we try to read segment != 0 from it. Of course > we shouldn't do that unless the display lied to us about what extension > blocks it provides. > > So I'm not sure if it would be better to trust that the display never > lies about the extension blocks, or if we should just assume all E-DDC > displays ack both segment addr and pointer. The no-ack feature seems > to there for backwards compatibility, for cases where the host always > sends the segment addr/pointer even when reading segment 0 (which your > code doesn't do). > > To handle it exactly as the spec says, I2C_M_IGNORE_NAK should be split > into two flags (one for addr, other for data). > > Hence i have split the i2c_msg into 3, segment pointer,offset(addr) > and data pointer. I was referring to the addr and data phases of the segment pointer. According to the spec the ack for the addr is always optional. But I suppose no sane device would nak the addr, while acking the data. -- Ville Syrjälä Intel OTC _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/dri-devel
