linux-kernel - Re: [PATCH v4 0/9] Migrate i8255 GPIO drivers to regmap API

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Date:   Mon, 5 Dec 2022 11:27:45 +0100
From:   Bartosz Golaszewski <brgl@...ev.pl>
To:     William Breathitt Gray <william.gray@...aro.org>
Cc:     linus.walleij@...aro.org, andriy.shevchenko@...ux.intel.com,
        linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org,
        michael@...le.cc, broonie@...nel.org
Subject: Re: [PATCH v4 0/9] Migrate i8255 GPIO drivers to regmap API

On Fri, Dec 2, 2022 at 5:27 PM William Breathitt Gray
<william.gray@...aro.org> wrote:
>
> Changes in v4:
>  - Align trailing '\' characters in macros to same column in 104-dio-48e
>    and 104-idi-48
>  - Remove superfluous trailing commas in macros in 104-dio-48e and
>    104-idi-48
>  - Simplify dio48e_handle_mask_sync() regmap_* calls error checks to
>    return error codes directly
>  - Refactor dio48e_irq_init_hw() for regmap and comment about spurious
>    interrupts; in theory this should be enough to prevent spurious
>    interrupts before the system is ready, but we can pass this function
>    as a callback where needed in the future
>  - Cleanup '{0}' as '{}' in probe() callbacks for 104-dio-48e,
>    104-idi-48, and gpio-mm
>  - Utilize dev_err_probe() in probe() callbacks for 104-dio-48e and
>    104-idi-48
>  - Provide convenience comments for idi48_regmap_irqs initialization
>    list
>  - Replace header includes with forward declarations in gpio-i8255.h
>
> The regmap API supports IO port accessors so we can take advantage of
> regmap abstractions rather than handling access to the device registers
> directly in the driver. The 104-dio-48e and gpio-mm modules depend on
> the i8255 library and are thus updated accordingly.
>
> The 104-IDI-48 is hardwired as an input-only device. Because the i8255
> control registers are not exposed on the 104-IDI-48, the i8255 library
> doesn't provide much benefit here. In this case it's simpler to utilize
> the gpio_regmap API directly, so this patch series does such and removes
> the i8255 library dependency from the 104-idi-48 module.
>
> The first patch in this series adjusts gpio_regmap to always set
> gpio_chip get_direction. This patch is mostly independent of the rest of
> the patches in the series and can be picked up separately if desired.
> I'm including it here because it allows the input-only 104-idi-48 driver
> to continue reporting offset directions after migrating to gpio_regmap.
>
> A handle_mask_sync() callback is introduced for the regmap_irq API. This
> is used by the 104-dio-48e driver to handle its enable/disable interrupt
> functionality. The 104-DIO-48E has a single register to handle
> enabling/disabling interrupts: a write of any value to this register
> enables interrupts, while any read disables interrupts.
>
> By leveraging the gpio_regmap API, the i8255 library is reduced to
> simply a devm_i8255_regmap_register() function, a configuration
> structure struct i8255_regmap_config, and a helper macro
> i8255_volatile_regmap_range() provided to simplify volatile PPI register
> hinting for the regmap.
>
> The regmap_irq API is leveraged by the 104-idi-48 and 104-dio-48e
> modules to support their IRQ functionality. Do their respective regmap
> configurations need use_hwlock set to true in this case, or is adequate
> locking already handled by the regmap_irq API?
>
> William Breathitt Gray (9):
>   gpio: regmap: Always set gpio_chip get_direction
>   regmap-irq: Add handle_mask_sync() callback
>   gpio: 104-dio-48e: Migrate to the regmap-irq API
>   gpio: 104-idi-48: Migrate to the regmap-irq API
>   gpio: 104-idi-48: Migrate to gpio-regmap API
>   gpio: i8255: Migrate to gpio-regmap API
>   gpio: 104-dio-48e: Migrate to regmap API
>   gpio: gpio-mm: Migrate to regmap API
>   gpio: i8255: Remove unused legacy interface
>
>  drivers/base/regmap/regmap-irq.c |  44 +++-
>  drivers/gpio/Kconfig             |   5 +-
>  drivers/gpio/gpio-104-dio-48e.c  | 391 ++++++++++---------------------
>  drivers/gpio/gpio-104-idi-48.c   | 336 +++++++++-----------------
>  drivers/gpio/gpio-gpio-mm.c      | 154 +++---------
>  drivers/gpio/gpio-i8255.c        | 320 +++++++------------------
>  drivers/gpio/gpio-i8255.h        |  54 ++---
>  drivers/gpio/gpio-regmap.c       |   7 +-
>  include/linux/regmap.h           |   5 +
>  9 files changed, 416 insertions(+), 900 deletions(-)
>
>
> base-commit: 3b7c7478eda00945987d45f902bc3942c89243d3
> --
> 2.38.1
>

It's pretty late in the release cycle and this touches several
existing drivers so I will not take it for v6.2. Please rebase and
resend once v6.3-rc1 is out.

Bart