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Date:   Wed, 23 Oct 2019 11:10:37 +0200
From:   "hch@lst.de" <hch@lst.de>
To:     Wei Hu <weh@microsoft.com>
Cc:     "b.zolnierkie@samsung.com" <b.zolnierkie@samsung.com>,
        KY Srinivasan <kys@microsoft.com>,
        Haiyang Zhang <haiyangz@microsoft.com>,
        Stephen Hemminger <sthemmin@microsoft.com>,
        "sashal@kernel.org" <sashal@kernel.org>, "hch@lst.de" <hch@lst.de>,
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        "robin.murphy@arm.com" <robin.murphy@arm.com>,
        "mchehab+samsung@kernel.org" <mchehab+samsung@kernel.org>,
        "sam@ravnborg.org" <sam@ravnborg.org>,
        "gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>,
        "alexandre.belloni@bootlin.com" <alexandre.belloni@bootlin.com>,
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        "dri-devel@lists.freedesktop.org" <dri-devel@lists.freedesktop.org>,
        "linux-fbdev@vger.kernel.org" <linux-fbdev@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-hyperv@vger.kernel.org" <linux-hyperv@vger.kernel.org>,
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        Michael Kelley <mikelley@microsoft.com>
Subject: Re: [PATCH] video: hyperv: hyperv_fb: Use physical memory for fb
 on HyperV Gen 1 VMs.
Message-ID: <20191023091037.GB21910@lst.de>
References: <20191022110905.4032-1-weh@microsoft.com>
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> +	select DMA_CMA

Thіs needs to be

	select DMA_CMA if HAVE_DMA_CONTIGUOUS

> +#include <linux/dma-contiguous.h>

> +	/* Allocate from CMA */
> +	// request_pages = (request_size >> PAGE_SHIFT) + 1;
> +	request_pages = (round_up(request_size, PAGE_SIZE) >> PAGE_SHIFT);
> +	page = dma_alloc_from_contiguous(NULL, request_pages, 0, false);

dma_alloc_from_contiguous is an internal helper, you must use it
through dma_alloc_coherent and pass a struct device to that function.

> +	if (!gen2vm) {
> +		pdev = pci_get_device(PCI_VENDOR_ID_MICROSOFT,
> +			PCI_DEVICE_ID_HYPERV_VIDEO, NULL);
> +		if (!pdev) {
> +			pr_err("Unable to find PCI Hyper-V video\n");
> +			return -ENODEV;
> +		}
> +	}

Please actually implement a pci_driver instead of hacks like this.

> +			par->need_docopy = false;
> +			goto getmem1;
> +		} else {

No need for an else after a goto.