On Wednesday, November 14, 2012 02:23:51 AM Moore, Robert wrote: > 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. Great, thanks! > > -----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 This is really quite a bit out-of-date as far as the memory allocation model.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. Yes, that would be really useful. Ideally, I'd like to be able to pass a pointer to an uninitialized buffer structure to it (or to a wrapper around it) and get a buffer full of struct acpi_resource objects (if _CRS returns any) back from it. :-) > > > > (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. Cool, thanks! > > > > (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. Well, I suppose I only wanted to say that acpi_free_buffer(buffer) would look a bit more straightforward than ACPI_FREE(buffer.pointer). :-) Thanks, Rafael -- I speak only for myself. Rafael J. Wysocki, Intel Open Source Technology Center. -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
