Re: git: 60381fd1ee86 - main - memdesc: Retire MEMDESC_CCB.

On 7/17/23 10:29 AM, Warner Losh wrote:
> On Mon, Jul 17, 2023 at 11:15 AM John Baldwin <jhb@freebsd.org> wrote:
> 
>> On 7/17/23 8:48 AM, Konstantin Belousov wrote:
>>> On Fri, Jul 14, 2023 at 06:41:03PM +0000, John Baldwin wrote:
>>>> The branch main has been updated by jhb:
>>>>
>>>> URL:
>> https://cgit.FreeBSD.org/src/commit/?id=60381fd1ee8668ea1e4676a6128883d987cab858
>>>>
>>>> commit 60381fd1ee8668ea1e4676a6128883d987cab858
>>>> Author:     John Baldwin <jhb@FreeBSD.org>
>>>> AuthorDate: 2023-07-14 18:30:31 +0000
>>>> Commit:     John Baldwin <jhb@FreeBSD.org>
>>>> CommitDate: 2023-07-14 18:32:16 +0000
>>>>
>>>>       memdesc: Retire MEMDESC_CCB.
>>>>
>>>>       Instead, change memdesc_ccb to examine the CCB and return a
>> memdesc of
>>>>       a more generic type describing the data buffer.
>>>
>>>> diff --git a/sys/kern/subr_bus_dma.c b/sys/kern/subr_bus_dma.c
>>>> index 65a08aeba17c..bfaad30b37d3 100644
>>>> --- a/sys/kern/subr_bus_dma.c
>>>> +++ b/sys/kern/subr_bus_dma.c
>>>> @@ -304,94 +304,6 @@ bus_dmamap_load_ma_triv(bus_dma_tag_t dmat,
>> bus_dmamap_t map,
>>>> @@ -566,49 +478,18 @@ bus_dmamap_load_ccb(bus_dma_tag_t dmat,
>> bus_dmamap_t map, union ccb *ccb,
>>>> +    mem = memdesc_ccb(ccb);
>>>> +    return (bus_dmamap_load_mem(dmat, map, &mem, callback,
>> callback_arg,
>>>> +        flags));
>>>>    }
>>> This makes kernel not linkable if CAM is not included into it.
>>
>> Hmmm, ok.  I can either move the memdesc_ccb routine into sys/kern
>> somewhere
>> (like the kern_memdesc.c file in my other pending review), or we can #ifdef
>> this function.  It probably doesn't make sense to have a
>> bus_dmamap_load_ccb
>> if you don't have CAM, so I think I prefer the second option.
>>
> 
> MINIMAL doesn't have CAM configured, but it is loadable as a module.
> 
> I'd think we'd want a dummy one fo these with weak symbol binding and have
> the actual
> one live in cam somewhere that overrides this  symbol.
> 
> I just hit this in building MINIMAL for other reasons....

Yeah, I was testing MINIMAL locally (which is still broken due to recent
TCP commits) to try out possible fixes.  One could possibly move
bus_dmamap_load_ccb into cam.ko entirely?  Especially this current version
doesn't really have any bus_dma-specific knowledge anymore but is just a
thin wrapper around bus_dmamap_load_mem:

int
bus_dmamap_load_ccb(bus_dma_tag_t dmat, bus_dmamap_t map, union ccb *ccb,
		    bus_dmamap_callback_t *callback, void *callback_arg,
		    int flags)
{
	struct ccb_hdr *ccb_h;
	struct memdesc mem;

	ccb_h = &ccb->ccb_h;
	if ((ccb_h->flags & CAM_DIR_MASK) == CAM_DIR_NONE) {
		callback(callback_arg, NULL, 0, 0);
		return (0);
	}

	mem = memdesc_ccb(ccb);
	return (bus_dmamap_load_mem(dmat, map, &mem, callback, callback_arg,
	    flags));
}

-- 
John Baldwin