Re: [PATCH 1/2] cdrom: gdrom: replace port I/O with MMIO accessors

[Adrian McMenamin]

On Sun, 5 Apr 2026 at 09:23, Florian Fuchs <fuchsfl@xxxxxxxxx> wrote:
>
> GDROM_DATA_REG is a memory-mapped data register, but the driver uses
> outsw() and insw() only for this register. Replace this with local
> helpers using MMIO accessors ioread16_rep() / iowrite16_rep().
>
> Before, it oopsed accessing the data register, as the io_port_base
> P2SEG gets added to the argument in outsw() / insw(), which leads to an
> unusable drive:
>
>         BUG: unable to handle kernel paging request at 405f7080
>         PC: [<8c28d5b4>] gdrom_spicommand+0x6c/0xb0
>
> Signed-off-by: Florian Fuchs <fuchsfl@xxxxxxxxx>
> ---
> The original Oops can be reproduced just by mounting a disc, like:
> mount -t iso9660 -o ro /dev/gdrom /mnt
> ---
>  drivers/cdrom/gdrom.c | 18 ++++++++++++++----
>  1 file changed, 14 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/cdrom/gdrom.c b/drivers/cdrom/gdrom.c
> index 4ba4dd06cbf4..dccf41fa5d0a 100644
> --- a/drivers/cdrom/gdrom.c
> +++ b/drivers/cdrom/gdrom.c
> @@ -171,6 +171,16 @@ static void gdrom_identifydevice(void *buf)
>                 data[c] = __raw_readw(GDROM_DATA_REG);
>  }
>
> +static void gdrom_fifo_readw(void *buf, unsigned int words)
> +{
> +       ioread16_rep((void __iomem *)GDROM_DATA_REG, buf, words);
> +}
> +
> +static void gdrom_fifo_writew(const void *buf, unsigned int words)
> +{
> +       iowrite16_rep((void __iomem *)GDROM_DATA_REG, buf, words);
> +}
> +
>  static void gdrom_spicommand(void *spi_string, int buflen)
>  {
>         short *cmd = spi_string;
> @@ -198,7 +208,7 @@ static void gdrom_spicommand(void *spi_string, int buflen)
>                 gdrom_getsense(NULL);
>                 return;
>         }
> -       outsw(GDROM_DATA_REG, cmd, 6);
> +       gdrom_fifo_writew(cmd, 6);
>  }
>


This is one of those "how did this ever work to begin with" bugs when
examined today - bur rather than introduce new local functions can we
not just use either readsw(p, d, l)/writesw(p, d, l) or
__raw_writew(p,d,l) and __raw_read(p,d,l) directly?

Adrian