Re: WARNING: drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c:364 vchiq_prepare_bulk_data

["Arnd Bergmann" <arnd@arndb.de>]

On Tue, Jun 11, 2024, at 13:37, Stefan Wahren wrote:
> Am 11.06.24 um 13:08 schrieb Arnd Bergmann:
>> On Tue, Jun 11, 2024, at 12:47, Stefan Wahren wrote:

>
>          if (len == 0)
>              pr_warn_once("%s: sg_dma_len() == 0\n", __func__);
>          else if (i && (i != (dma_buffers - 1)) && (len & ~PAGE_MASK))
>              pr_warn_once("%s: following block not page aligned\n",
> __func__);
>          else if (i && (addr & ~PAGE_MASK)) {
>              pr_warn_once("%s: block %u, DMA address %pad doesn't align
> with PAGE_MASK 0x%lx\n", __func__, i, &addr, PAGE_MASK);
>              pr_warn_once("sg_dma_is_swiotlb: %d, dma_flags: %x\n",
> sg_dma_is_swiotlb(sg), sg->dma_flags);
>              pr_warn_once("type = %s\n", (type == PAGELIST_WRITE) ?
> "PAGELIST_WRITE" : "PAGELIST_READ");
>              if (buf)
>                  pr_warn_once("buf = %p, count = %zu\n", buf, count);
>              else
>                  pr_warn_once("ubuf = %p, count = %zu\n", ubuf, count);
>          }
>
> Output:
>
> [   66.184030] create_pagelist: block 1, DMA address 0x00000000f5fc7800
> doesn't align with PAGE_MASK 0xfffffffffffff000
> [   66.184056] sg_dma_is_swiotlb: 0, dma_flags: 0
> [   66.184063] type = PAGELIST_READ
> [   66.184066] ubuf = 00000000266a70a7, count = 0

From my reading of the code, it's not really meant to handle
count=0, so maybe the answer for that is to just return an
error (or possibly success) when there is data attached to
the request from user space, something like

--- a/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_dev.c
+++ b/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_dev.c
@@ -328,6 +328,11 @@ static int vchiq_irq_queue_bulk_tx_rx(struct vchiq_instance *instance,
                userdata = args->userdata;
        }
 
+       if (!args->size) {
+               ret = 0;
+               goto out;
+       }
+
        status = vchiq_bulk_transfer(instance, args->handle, NULL, args->data, args->size,
                                     userdata, args->mode, dir);