2022-11-29 15:58:36

by Bjorn Helgaas

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 <[email protected]>
> ---
> 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

2022-12-13 14:50:03

by Sven Zühlsdorf

Subject: Re: [PATCH] HID: mcp2221: Fix GPIO output handling

On Tue, 29 Nov 2022, Bjorn Helgaas wrote:
> [+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 <[email protected]>
>> ---
>> 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
>

I can confirm that the order is reversed when compared to both the data sheet
and what I can observe in the hid reports.
The patch from the linked bugzilla bug fixes the issue for me.

> --- a/drivers/hid/hid-mcp2221.c
> +++ b/drivers/hid/hid-mcp2221.c
> @@ -74,8 +74,8 @@ struct mcp_get_gpio {
> u8 cmd;
> u8 dummy;
> struct {
> - u8 direction;
> u8 value;
> + u8 direction;
> } gpio[MCP_NGPIO];
> } __packed;

Tested-by: Sven Zühlsdorf <[email protected]>