linux-kernel - Re: [PATCH 1/3] media/ttusb-budget: remove pci_zalloc

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Date:   Tue, 09 Jan 2018 12:49:26 -0800
From:   Joe Perches <joe@...ches.com>
To:     Christoph Hellwig <hch@....de>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>
Cc:     linux-pci@...r.kernel.org, linux-media@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] media/ttusb-budget: remove pci_zalloc_coherent abuse

On Tue, 2018-01-09 at 21:39 +0100, Christoph Hellwig wrote:
> Switch to a plain kzalloc instea of pci_zalloc_coherent to allocate
> memory for the USB DMA.
[]
> diff --git a/drivers/media/usb/ttusb-budget/dvb-ttusb-budget.c b/drivers/media/usb/ttusb-budget/dvb-ttusb-budget.c
[]
> @@ -792,21 +791,15 @@ static void ttusb_free_iso_urbs(struct ttusb *ttusb)
> []
>  static int ttusb_alloc_iso_urbs(struct ttusb *ttusb)
>  {
>  	int i;
>  
> -	ttusb->iso_buffer = pci_zalloc_consistent(NULL,
> -						  ISO_FRAME_SIZE * FRAMES_PER_ISO_BUF * ISO_BUF_COUNT,
> -						  &ttusb->iso_dma_handle);
> -
> +	ttusb->iso_buffer = kzalloc(ISO_FRAME_SIZE * FRAMES_PER_ISO_BUF *
> +			ISO_BUF_COUNT, GFP_KERNEL);
>  	if (!ttusb->iso_buffer) {
>  		dprintk("%s: pci_alloc_consistent - not enough memory\n",
>  			__func__);

This message doesn't make sense anymore and it might as well
be deleted.

And it might be better to use kcalloc

	ttusb->iso_buffer = kcalloc(FRAMES_PER_ISO_BUF * ISO_BUF_COUNT,
				    ISO_FRAME_SIZE, GFP_KERNEL);