Re: [PATCH v2 5/6] esp_scsi: De-duplicate PIO routines

[Christoph Hellwig]

On Tue, Oct 16, 2018 at 10:52:26AM +1100, Finn Thain wrote:
> True enough. We agree that this #ifdef is undesirable. And yet when I 
> tried it, I found an unexpected readability benefit to your suggestion:
> 
> #ifdef CONFIG_SCSI_ESP_PIO
>         u8 __iomem              *fifo_reg;
>         int                     send_cmd_error;
>         u32                     send_cmd_residual;
> #endif
> 
> This grouping does help convey the purpose of these struct members, even 
> though the #ifdef is meant for the compiler not for the human reader.
> 
> So maybe it makes sense to group these definitions (they are all the same 
> size):
> 
>         /* These are used by esp_scsi_send_pio_cmd() */
>         u8 __iomem              *fifo_reg;
>         int                     send_cmd_error;
>         u32                     send_cmd_residual;

I like the grouping, and in fact the ifdef sounds fine to me as well.

> Do static checkers really complain about this? I think the validity of an 
> extern can't be known until the final linkage is done.

None that I know of does, and as said before this patterns is very
common all over the kernel.