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Date:   Thu, 13 Jun 2019 09:39:00 +0200
From:   Christoph Hellwig <hch@lst.de>
To:     Alan Stern <stern@rowland.harvard.edu>
Cc:     Christoph Hellwig <hch@lst.de>, Oliver Neukum <oneukum@suse.com>,
        "iommu@lists.linux-foundation.org" <iommu@lists.linux-foundation.org>,
        Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>,
        "linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
        Linux-Renesas <linux-renesas-soc@vger.kernel.org>,
        "linux-usb@vger.kernel.org" <linux-usb@vger.kernel.org>
Subject: Re: How to resolve an issue in swiotlb environment?
Message-ID: <20190613073900.GC12093@lst.de>
References: <20190612120653.GA25285@lst.de> <Pine.LNX.4.44L0.1906121038210.1557-100000@iolanthe.rowland.org>
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On Wed, Jun 12, 2019 at 10:43:11AM -0400, Alan Stern wrote:
> Would it be okay to rely on the assumption that USB block devices never 
> have block size < 512?  (We could even add code to the driver to 
> enforce this, although refusing to handle such devices at all might be 
> worse than getting an occasional error.)

sd.c only supports a few specific sector size, and none of them is
< 512 bytes:

	if (sector_size != 512 &&
	    sector_size != 1024 &&
	    sector_size != 2048 &&
	    sector_size != 4096) {
	    	...
		sdkp->capacity = 0;