Re: [libgpiod][PATCH v3] treewide: rework struct gpiod_line_bulk

[Bartosz Golaszewski <bgolaszewski@xxxxxxxxxxxx>]

On Fri, Oct 30, 2020 at 3:23 PM Bartosz Golaszewski <brgl@xxxxxxxx> wrote:
>
> From: Bartosz Golaszewski <bgolaszewski@xxxxxxxxxxxx>
>
> Current implementation of struct gpiod_line_bulk uses stack memory
> excessively. The structure is big: it's an array 64 pointers + 4 bytes
> size. That amounts to 260 bytes on 32-bit and 516 bytes on 64-bit
> architectures respectively. It's also used everywhere as all functions
> dealing with single lines eventually end up calling bulk counterparts.
>
> The rework addresses it by making the bulk structure opaque and
> providing appropriate interfaces for library users while retaining a way
> for internal users to allocate single line bulks on the stack.
>
> The macro-based loop has been removed. In its place we provide a function
> iterating over all lines held by a bulk and calling the provided callback
> function for each line.
>
> Since bulk operations can now fail, a bunch of test-cases has been added
> to cover the relevant code.
>
> While at it: using the word offset both when referring to line's HW
> offset in a chip as well as the offset in a bulk leads to confusion.
> This patch renames the bulk offset to index.
>
> Some additional improvements to the patch by:
>   Kent Gibson <warthog618@xxxxxxxxx>
>
> Signed-off-by: Bartosz Golaszewski <bgolaszewski@xxxxxxxxxxxx>
> ---
> v1 -> v2:
> - make offset -> index in all bulk-related interfaces and docs
> - drop the owner chip reference from struct gpiod_line_bulk and reuse the
>   owner of the first line
> - drop bulk_same_chip helper
>
> v2 -> v3:
> - drop bulk iterators in favor of looping over bulk indices
>

Applied this patch. We can add some tweaks later.

Bartosz