Rafael, I sounds like with a few changes, we can enhance this mechanism to be more useful to you and others. Some comments below. I need to look at the code in question a bit more, but I see no insurmountable issues. Bob > -----Original Message----- > From: Rafael J. Wysocki [mailto:rjw@xxxxxxx] > Sent: Tuesday, November 13, 2012 2:57 PM > To: Moore, Robert > Cc: Mika Westerberg; mathias.nyman@xxxxxxxxxxxxxxx; linux- > acpi@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; lenb@xxxxxxxxxx; > Wysocki, Rafael J; broonie@xxxxxxxxxxxxxxxxxxxxxxxxxxx; > grant.likely@xxxxxxxxxxxx; linus.walleij@xxxxxxxxxx; khali@xxxxxxxxxxxx; > Bjorn Helgaas; Zheng, Lv > Subject: Re: [PATCH 3/3] ACPI: Evaluate _CRS while creating device node > objects > > On Tuesday, November 13, 2012 10:06:03 PM Moore, Robert wrote: > > I may not quite understand what you are asking for, but I will try. > > It seems like we already have much of what you want/need, so maybe I'm > > missing something. > > I think all of the necessary pieces are there. > > > > So what I would like to have, in general terms, is something like > > > acpi_walk_resources() split into three parts: > > > > > > (1) One that processes the _CRS output and creates a list of > > > struct acpi_resource objects for us to play with. I suppose > > > it's OK if that's just a buffer filled with resource objects, > > > but a linked list might be more convenient. > > > > > > > This sounds like AcpiGetCurrentResources. It executes _CRS and formats > > the data into acpi_resource objects. > > Yes, it does. However, it is not completely clear to me if/how the caller > is supposed to prepare the buffer object pointed to by the second arg. > > If the buffer is initialized by AcpiGetCurrentResources, then that's what > I need for (1). It looks to me that at least AcpiGetCurrentResources does not actually ever allocate a buffer for the resource template, it expects the caller to eventually provide one of at least the size of the returned resource template. This is really quite a bit out-of-date as far as the memory allocation model. It should also support the option to just allocate the buffer of the appropriate size before returning it to the caller. > > > > (2) One that allows us to access (read/write) resources in the > > > list returned by (1). We don't need to open code walking > > > the list and I probably wouldn't event want to do that. What > > > we need is to be able to walk the same list for a number of > > > times and possibly to modify values in the resource objects > > > if there are conflicts. > > > > This sounds like AcpiWalkResources. I suppose a possible issue is that > > currently, AcpiWalkResources actually invokes the _CRS, _PRS, or _AEI > > method on behalf of the caller. > > Yes, that exactly is the problem. > > > It might make more sense to allow the caller to pass in the resource > > buffer returned from a call to _CRS, etc. > > Yes! :-) I'll take a closer look at this tomorrow. > > > > > > > (3) One allowing us to free the list returned by (1) if not needed > > > any more. > > > > > > > AcpiGetCurrentResources: Currently, everything is returned in a single > > buffer to minimize the number of allocations. A buffer you can free > > when you are done with it. > > I suppose I should use ACPI_FREE(buffer.pointer) for that, but isn't it > for the ACPICA's internal use only? > > Besides, I would prefer to be able to pass just "buffer" for freeing, > without having to touch its internals. No big deal, but it would be > nicer. :-) The ACPI_BUFFER type is in fact a public type that is meant to return both the buffer and the (actual) length. You will find many instances of ACPI_FREE(buffer.pointer) within existing linux code, since it also used for objects returned by control method execution/object evaluation. > > > I think I saw where you mentioned that you cannot copy this buffer > > because of internal pointers to other areas of the buffer. Yes. > > However, we can build linked lists all day if you really want them :-) > > I really won't care if I can pass a resource buffer to a "walker" routine. > :-) > > > > And it would be great if we could take the list returned by (1), > > > modify the resources in it and feed it back to _SRS (after > > > conversion back to the format that _SRS understands). > > > > > > > AcpiSetCurrentResources. > > > > The AML debugger already has a command that illustrates the use of the > > various resource interfaces, see dbcmds.c > > I will. > > Thanks, > Rafael > > > -- > I speak only for myself. > Rafael J. Wysocki, Intel Open Source Technology Center. ��.n��������+%������w��{.n�����{�����ܨ}���Ơz�j:+v�����w����ޙ��&�)ߡ�a����z�ޗ���ݢj��w�f
