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SubjectRe: [PATCH] fbtft: limit transfer length by spi device limit
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Den 26.05.2016 21:25, skrev Michal Suchanek:
> Some SPI controllers can transfer only small piece of data at a time.
> Since SPI core gained a function to get the maximum transfer length use
> it.
>
> Signed-off-by: Michal Suchanek <hramrach@gmail.com>
> ---
>
> Tested on sunxi spi with DMA enabled and disabled. Makes a visible speed
> difference and display works in either case.
>
> drivers/staging/fbtft/fbtft-core.c | 9 +++++++++
> 1 file changed, 9 insertions(+)
>
> diff --git a/drivers/staging/fbtft/fbtft-core.c b/drivers/staging/fbtft/fbtft-core.c
> index 0c1a77c..f3bdc8f 100644
> --- a/drivers/staging/fbtft/fbtft-core.c
> +++ b/drivers/staging/fbtft/fbtft-core.c
> @@ -1346,6 +1346,15 @@ int fbtft_probe_common(struct fbtft_display *display,
> return PTR_ERR(pdata);
> }
>
> + if (sdev && (spi_max_transfer_size(sdev) < SIZE_MAX))
> + if ((pdata->txbuflen <= 0) || (pdata->txbuflen > spi_max_transfer_size(sdev))) {
> + dev_warn(dev,
> + "Limiting used buffer size %i -> %i due to device %s transfer size limitation",
> + pdata->txbuflen, spi_max_transfer_size(sdev),
> + dev_name(&sdev->dev));
> + pdata->txbuflen = spi_max_transfer_size(sdev);
> + }
> +
> info = fbtft_framebuffer_alloc(display, dev, pdata);
> if (!info)
> return -ENOMEM;

(Ugh, this code of mine looks worse each time I'm confronted with it.)

You have even taken care of the special txbuflen == -1 value I see,
so I guess this is as good as it gets without any major refactoring, so:

Acked-by: Noralf Trønnes <noralf@tronnes.org>

And there's no point in doing any refactoring since I'm working on a DRM
successor for fbtft. I have been working on it since the fbdev maintainer
issued the "No more new fbdev drivers, please" call in September and now
it has reached a tipping point where I can say that I will keep working
on it until it's done.
Some info: https://github.com/notro/tinydrm/wiki

Thanks,
Noralf.

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