From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:43607) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1VrACz-0003zk-E1 for qemu-devel@nongnu.org; Thu, 12 Dec 2013 12:38:02 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1VrACu-0004Bq-IL for qemu-devel@nongnu.org; Thu, 12 Dec 2013 12:37:57 -0500 Received: from mail-pd0-f173.google.com ([209.85.192.173]:52573) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1VrACu-00049m-Bv for qemu-devel@nongnu.org; Thu, 12 Dec 2013 12:37:52 -0500 Received: by mail-pd0-f173.google.com with SMTP id p10so879074pdj.4 for ; Thu, 12 Dec 2013 09:37:51 -0800 (PST) MIME-Version: 1.0 In-Reply-To: References: <1386279359-32286-1-git-send-email-roy.franz@linaro.org> <1386279359-32286-6-git-send-email-roy.franz@linaro.org> From: Peter Maydell Date: Thu, 12 Dec 2013 17:37:31 +0000 Message-ID: Content-Type: text/plain; charset=UTF-8 Subject: Re: [Qemu-devel] [PATCH V5 5/7] Add max device width parameter for NOR devices List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Roy Franz Cc: Kevin Wolf , QEMU Developers , Stefan Hajnoczi , Patch Tracking On 12 December 2013 17:26, Peter Maydell wrote: > On 5 December 2013 21:35, Roy Franz wrote: >> For handling CFI and device ID reads, we need to not only know the >> width that a NOR flash device is configured for, but also its maximum >> width. The maximum width addressing mode is used for multi-width >> parts no matter which width they are configured for. The most common >> case is x16 parts that also support x8 mode. When configured for x8 >> operation these devices respond to CFI and device ID requests differently >> than native x8 NOR parts. > >> DEFINE_PROP_UINT64("sector-length", struct pflash_t, sector_len, 0), >> DEFINE_PROP_UINT8("width", struct pflash_t, bank_width, 0), >> DEFINE_PROP_UINT8("device-width", struct pflash_t, device_width, 0), >> + DEFINE_PROP_UINT8("max-device-width", struct pflash_t, max_device_width, 0), > > So I think that given we now have three width related properties > we could use a comment here about what they mean. Do I have > this right? > > /* width here is the overall width of this QEMU device in bytes. > * The QEMU device may be emulating a number of flash devices > * wired up in parallel; the width of each individual flash > * device should be specified via device-width. If the individual > * devices have a maximum width which is greater than the width > * they are being used for, this maximum width should be set via > * max-device-width (which otherwise defaults to device-width). > * So for instance a 32-bit wide QEMU flash device made from four > * 16-bit flash devices used in 8-bit wide mode would be configured > * with width = 4, device-width = 1, max-device-width = 2. > * > * If device-width is not specified we default to backwards > * compatible behaviour which is a bad emulation of two > * 16 bit devices making up a 32 bit wide QEMU device. This > * is deprecated for new uses of this device. > */ PS: if you're happy that the comment above is correct, I can just add it locally (and fix up the format nits in the other patch), to save you having to respin the series, and stick it in the target-arm.next queue. thanks -- PMM