Re: [RFC] ahci(4) patch

On Wed, Nov 16, 2011 at 2:59 PM, Alexander Motin <mav_at_freebsd.org> wrote:
> On 17.11.2011 00:44, Maksim Yevmenkin wrote:
>>
>> On Wed, Nov 16, 2011 at 2:35 PM, Alexander Motin<mav_at_freebsd.org>  wrote:
>>>
>>> On 16.11.2011 23:59, Maksim Yevmenkin wrote:
>>>>
>>>> would anyone object to the following ahci(4) patch?
>>>>
>>>> ==
>>>>
>>>> --- ahci.c.orig 2011-11-16 21:35:26.000000000 +0000
>>>> +++ ahci.c      2011-11-16 21:35:41.000000000 +0000
>>>> _at__at_ -500,7 +500,7 _at__at_
>>>>        for (unit = 0; unit<    ctlr->channels; unit++) {
>>>>                if ((ctlr->ichannels&    (1<<    unit)) == 0)
>>>>                        continue;
>>>> -               child = device_add_child(dev, "ahcich", -1);
>>>> +               child = device_add_child(dev, "ahcich", unit);
>>>>                if (child == NULL)
>>>>                        device_printf(dev, "failed to add channel
>>>> device\n");
>>>>                else
>>>>
>>>> ==
>>>>
>>>> the idea is to have "static" numbering for ada(4) disks.
>>>
>>> I do. The only way I see this useful is if you have BIOS configured for
>>> non-hot-swappable disks, in which case you have some AHCI channels
>>> disabled,
>>> but want to keep numbers of the rest. While I don't like this mode in
>>> general, especially when it can't be disabled, that patch could be useful
>>> in
>>> these cases. But in other cases, when you have several AHCI controllers,
>>> it
>>> just wont not work. You will receive error on attempt to create second
>>> ahcich0.
>>
>> shouldn't achcichX be destroyed when disk is detached/removed/etc.?
>
> List of implemented AHCI channels to expose as ahcichX set by BIOS in
> vendor-specific way, but only during boot and not by many BIOSes. Destroying
> them on disk detach theoretically possible, but IMHO not right, as bus
> doesn't disappear on disk disconnect.
>
>> the particular problem i'm trying to address is disk re-numbering when
>> one of the disks fails/removed/etc. i'm trying to use hints to wire
>> disks to controllers/busses. it works perfectly fine with da(4) disks
>> (even hot swappable ones) , but i can not make it to work with ada(4)
>> disks. i'm perfectly fine to hid this under some sort of option
>> (something similar to ATA_STATIC_ID, AHCI_STATIC_ID for example)
>
> Wiring works for adaX also, unless your BIOS is so "intelligent" to report
> unconnected ports and not impliemented.. You should just wire CAM buses to
> ahcichX, not to ahciX. It could be done in other way changing just by one
> line around xpt_bus_register(), but now it is done so.

ok. then i must be missing something, here is what i have in device.hints

hint.scbus.0.at="umass-sim0"
hint.scbus.1.at="ahcich0"
hint.scbus.2.at="ahcich1"
hint.scbus.3.at="ahcich2"
hint.scbus.4.at="ahcich3"
hint.scbus.5.at="ahcich4"
hint.scbus.6.at="ahcich5"

hint.da.0.at="scbus0"
hint.ada.0.at="scbus1"
hint.ada.1.at="scbus2"
hint.ada.2.at="scbus3"
hint.ada.3.at="scbus4"
hint.ada.4.at="scbus5"
hint.ada.5.at="scbus6"

this is for 6-port ahci(4) compatible controller (intel) on the
motherboard. no matter which achi(4) ports are connected, resulted
adaX devices are always sequential starting from ada0. so, the
question is: what am i doing wrong here?

thanks,
max