linux-kernel - Re: [PATCH] HID: mcp2221: Fix GPIO output handling

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Date:   Tue, 29 Nov 2022 09:39:33 -0600
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Lars Povlsen <lars.povlsen@...rochip.com>
Cc:     Rishi Gupta <gupt21@...il.com>, Jiri Kosina <jikos@...nel.org>,
        Benjamin Tissoires <benjamin.tissoires@...hat.com>,
        UNGLinuxDriver <UNGLinuxDriver@...rochip.com>,
        linux-i2c@...r.kernel.org, linux-input@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Takayuki 'January June' Suwa <jjsuwa_sys3175@...oo.co.jp>
Subject: Re: [PATCH] HID: mcp2221: Fix GPIO output handling

[+cc Takayuki, thanks for your report!]

On Wed, Nov 04, 2020 at 11:02:23PM +0100, Lars Povlsen wrote:
> The mcp2221 driver GPIO output handling has has several issues.
> 
> * A wrong value is used for the GPIO direction.
> 
> * Wrong offsets are calculated for some GPIO set value/set direction
>   operations, when offset is larger than 0.
> 
> This has been fixed by introducing proper manifest constants for the
> direction encoding, and using 'offsetof' when calculating GPIO
> register offsets.
> 
> The updated driver has been tested with the Sparx5 pcb134/pcb135
> board, which has the mcp2221 device with several (output) GPIO's.
> 
> Signed-off-by: Lars Povlsen <lars.povlsen@...rochip.com>
> ---
>  drivers/hid/hid-mcp2221.c | 48 +++++++++++++++++++++++++++++++--------
>  1 file changed, 39 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/hid/hid-mcp2221.c b/drivers/hid/hid-mcp2221.c
> index 0d27ccb55dd9..4211b9839209 100644
> --- a/drivers/hid/hid-mcp2221.c
> +++ b/drivers/hid/hid-mcp2221.c

> +/* MCP GPIO get command layout */
> +struct mcp_get_gpio {
> +	u8 cmd;
> +	u8 dummy;
> +	struct {
> +		u8 direction;
> +		u8 value;
> +	} gpio[MCP_NGPIO];
> +} __packed;

This bug report: https://bugzilla.kernel.org/show_bug.cgi?id=216736
suggests that direction and value may be reversed here.

Mentioning here in case nobody actively monitors the bugzilla.

Bjorn