linux-kernel - Re: [PATCH] hte: tegra194: improve the GPIO-related comment

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Date:   Fri, 29 Sep 2023 14:38:36 -0700
From:   Dipen Patel <dipenp@...dia.com>
To:     Bartosz Golaszewski <brgl@...ev.pl>,
        Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>
Cc:     timestamp@...ts.linux.dev, linux-tegra@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Bartosz Golaszewski <bartosz.golaszewski@...aro.org>,
        Linus Walleij <linus.walleij@...aro.org>
Subject: Re: [PATCH] hte: tegra194: improve the GPIO-related comment

On 9/11/23 2:44 AM, Bartosz Golaszewski wrote:
> From: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
> 
> Using any of the GPIO interfaces using the global numberspace is
> deprecated. Make it clear in the comment.
> 
> Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
> Acked-by: Linus Walleij <linus.walleij@...aro.org>
> ---
> This was part of a wider series but since this is independent, I'm sending
> it separately.
> 
>  drivers/hte/hte-tegra194.c | 13 ++++++++-----
>  1 file changed, 8 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/hte/hte-tegra194.c b/drivers/hte/hte-tegra194.c
> index 6fe6897047ac..9fd3c00ff695 100644
> --- a/drivers/hte/hte-tegra194.c
> +++ b/drivers/hte/hte-tegra194.c
> @@ -407,12 +407,15 @@ static int tegra_hte_line_xlate(struct hte_chip *gc,
>  		return -EINVAL;
>  
>  	/*
> +	 * GPIO consumers can access GPIOs in two ways:
>  	 *
> -	 * There are two paths GPIO consumers can take as follows:
> -	 * 1) The consumer (gpiolib-cdev for example) which uses GPIO global
> -	 * number which gets assigned run time.
> -	 * 2) The consumer passing GPIO from the DT which is assigned
> -	 * statically for example by using TEGRA194_AON_GPIO gpio DT binding.
> +	 * 1) Using the global GPIO numberspace.
> +	 *
> +	 * This is the old, now DEPRECATED method and should not be used in
> +	 * new code. TODO: Check if tegra is even concerned by this.
This use case is to do namespace mapping from gpio subsystem to hte. Few doubts:
1. What does deprecate mean here? Does gpio subsys not use global space anymore?
2. If yes, what GPIO number is set when it comes from gpiolib-cdev, as based on that I may have to
reflect in the mapping, tegra194_aon_gpio_map for example.
> +	 *
> +	 * 2) Using GPIO descriptors that can be assigned to consumer devices
> +	 * using device-tree, ACPI or lookup tables.
>  	 *
>  	 * The code below addresses both the consumer use cases and maps into
>  	 * HTE/GTE namespace.