Re: [PATCH v2 2/6] esp_scsi: Track residual for PIO transfers

Finn Thain
2018-10-14T22:14:25Z

On Sun, 14 Oct 2018, Geert Uytterhoeven wrote:

>
> > Fixes: 6fe07aaffbf0
>
> Fixes: 6fe07aaffbf0 ("[SCSI] m68k: new mac_esp scsi driver")
>

Fixed.

> > Tested-by: Stan Johnson <userm57@yahoo.com>
> > Signed-off-by: Finn Thain <fthain@telegraphics.com.au>
> > Tested-by: Michael Schmitz <schmitzmic@gmail.com>
>
> > --- a/drivers/scsi/esp_scsi.h
> > +++ b/drivers/scsi/esp_scsi.h
> > @@ -540,6 +540,8 @@ struct esp {
> >
> > void *dma;
> > int dmarev;
> > +
> > + int send_cmd_residual;
>
> unsigned int?
>

My first thought was to use u32, same as esp_count. But it turns out that
the end result really is an int --

static int esp_data_bytes_sent(struct esp *esp, struct esp_cmd_entry *ent,
struct scsi_cmnd *cmd)
{
int fifo_cnt, ecount, bytes_sent, flush_fifo;

...
bytes_sent = esp->data_dma_len;
bytes_sent -= ecount;
bytes_sent -= esp->send_cmd_residual;
...
return bytes_sent;
}

Apparently over/underflow is a real possibility, because there is a test
for this in esp_process_event().

--

> Gr{oetje,eeting}s,
>
> Geert
>
> --
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
>
> In personal conversations with technical people, I call myself a hacker. But
> when I'm talking to journalists I just say "programmer" or something like that.
> -- Linus Torvalds
>