Re: [PATCH v7 1/2] spi: Unify error codes by replacing -ENOTSUPP with -EOPNOTSUPP

[Miquel Raynal <miquel.raynal@xxxxxxxxxxx>]

Hello,

acelan.kao@xxxxxxxxxxxxx wrote on Wed, 29 Nov 2023 14:43:10 +0800:

> From: "Chia-Lin Kao (AceLan)" <acelan.kao@xxxxxxxxxxxxx>
> 
> This commit updates the SPI subsystem, particularly affecting "SPI MEM"
> drivers and core parts, by replacing the -ENOTSUPP error code with
> -EOPNOTSUPP.
> 
> The key motivations for this change are as follows:
> 1. The spi-nor driver currently uses EOPNOTSUPP, whereas calls to spi-mem
> might return ENOTSUPP. This update aims to unify the error reporting
> within the SPI subsystem for clarity and consistency.
> 
> 2. The use of ENOTSUPP has been flagged by checkpatch as inappropriate,
> mainly being reserved for NFS-related errors. To align with kernel coding
> standards and recommendations, this change is being made.
> 
> 3. By using EOPNOTSUPP, we provide more specific context to the error,
> indicating that a particular operation is not supported. This helps
> differentiate from the more generic ENOTSUPP error, allowing drivers to
> better handle and respond to different error scenarios.
> 
> Risks and Considerations:
> While this change is primarily intended as a code cleanup and error code
> unification, there is a minor risk of breaking user-space applications
> that rely on specific return codes for unsupported operations. However,
> this risk is considered low, as such use-cases are unlikely to be common
> or critical. Nevertheless, developers and users should be aware of this
> change, especially if they have scripts or tools that specifically handle
> SPI error codes.
> 
> This commit does not introduce any functional changes to the SPI subsystem
> or the affected drivers.
> 
> Signed-off-by: Chia-Lin Kao (AceLan) <acelan.kao@xxxxxxxxxxxxx>
> 
> ---
> v5. distinguish -EOPNOTSUPP from -ENOTSUPP
> v6. a. spi_nor_set_4byte_addr_mode() should check -EOPNOTSUPP, all
>        callbacks of set_4byte_addr_mode() will eventually return
>        -EOPNOTSUPP if the checking failed.
>     b. Update comment to describe the reason for the patch and the
>        affected parts.
>     c. Update the kernel-doc of exec_op() in struct spi_controller_mem_ops
> v7. added comment for the return code changes may affect userspace, and
>     the risk after this change
> ---

Looks sensible to me, let's make the conversion.

Acked-by: Miquel Raynal <miquel.raynal@xxxxxxxxxxx>

Thanks,
Miquèl