Re: [PARPORT] ECP mode transfers in 2.4.x kernels

From: Philip Blundell (
Date: Wed Aug 29 2001 - 16:46:38 EDT

  • Next message: Dave Strauss: "Re: [PARPORT] ECP mode transfers in 2.4.x kernels"

    >Is there any way for the lp driver to tell the parport driver whether
    >or not to use DMA? I'm pretty sure this is not a long-term solution
    >to the problem but I'd like to try it.

    Don't think so. If you just want a quick hack, you can try removing the
    assignment to p->ops->compat_write_data in this code from parport_pc:

            if (p->dma != PARPORT_DMA_NOFIFO &&
                priv->fifo_depth > 0 && p->irq != PARPORT_IRQ_NONE) {
                    p->ops->compat_write_data = parport_pc_compat_write_block_pio;
    #ifdef CONFIG_PARPORT_1284
                    p->ops->ecp_write_data = parport_pc_ecp_write_block_pio;
                    /* currently broken, but working on it.. (FB) */
                    /* p->ops->ecp_read_data = parport_pc_ecp_read_block_pio; */
    #endif /* IEEE 1284 support */

    >Beyond that, has anyone seen any similar problems? Any ideas for things
    >to try?

    I haven't heard of similar problems, but I suspect the DMA-assisted
    compatibility mode stuff hasn't seen all that much testing.

    What kind of failure are you seeing -- is it just the same sort of
    non-specific corruption you were getting in the software ECP case?


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