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

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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@xxxxxxxxx>
Signed-off-by: Finn Thain <fthain@xxxxxxxxxxxxxxxxxxx>
Tested-by: Michael Schmitz <schmitzmic@xxxxxxxxx>

--- 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@xxxxxxxxxxxxxx

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




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