From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:40434) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aTYVP-0000rs-1M for qemu-devel@nongnu.org; Wed, 10 Feb 2016 12:24:44 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1aTYVK-0000dp-TB for qemu-devel@nongnu.org; Wed, 10 Feb 2016 12:24:42 -0500 Received: from mx2.parallels.com ([199.115.105.18]:54053) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aTYVK-0000dM-NY for qemu-devel@nongnu.org; Wed, 10 Feb 2016 12:24:38 -0500 Date: Wed, 10 Feb 2016 20:24:21 +0300 From: Roman Kagan Message-ID: <20160210172420.GH9169@rkaganb.sw.ru> References: <1454612376-7072-1-git-send-email-mst@redhat.com> <1454612376-7072-49-git-send-email-mst@redhat.com> <20160205192507.41fc6024@nial.brq.redhat.com> <20160208131443.GC6420@rkaganb.sw.ru> <56B8F89F.3090603@redhat.com> <20160209155249.GA13787@rkaganb.sw.ru> <56BA1229.8090809@redhat.com> <56BA319C.9010505@redhat.com> <20160209204743-mutt-send-email-mst@redhat.com> <56BB61E6.1090500@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <56BB61E6.1090500@redhat.com> Subject: Re: [Qemu-devel] [PULL 48/49] i386: populate floppy drive information in DSDT List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: John Snow Cc: Peter Maydell , Eduardo Habkost , "Michael S. Tsirkin" , qemu-devel@nongnu.org, Paolo Bonzini , Igor Mammedov , Laszlo Ersek , Richard Henderson On Wed, Feb 10, 2016 at 11:14:30AM -0500, John Snow wrote: > On 02/09/2016 01:48 PM, Michael S. Tsirkin wrote: > > On Tue, Feb 09, 2016 at 07:36:12PM +0100, Laszlo Ersek wrote: > >> Implementing this in QEMU would require: > >> - inventing virt-only registers for the FDC that provide the current > >> disk geometry, > > We do secretly have these registers, but of course there's no spec to > interpreting what they mean. For instance, what do they read when the > drive is empty? I am not sure that information is codified in the ACPI spec. There are various possibilities, like returning False for the corresponding drive in _FDE (Floppy Disk Enumerate) object, or returning 0 aka unknown as drive type in _FDI. Anyway I'd hate needing to expose all of that in an ACPI-accessible form, this is going to become too fat. > Could be wrong, you seemed to indicate that the ACPI spec said that the > info matches what you get from a certain legacy bios routine, but I > don't know the specifics of that routine, either. Indeed, it's supposed to do the same as https://en.wikipedia.org/wiki/INT_13H#INT_13h_AH.3D08h:_Read_Drive_Parameters and, as I wrote in another mail, the SeaBIOS implementation here is rather simplistic. > Roman, does the 0xFF "empty disk geometry" hack appear to work for > Windows 10? > > Maybe it's fine enough as-is, as per Laszlo's good synopsis here. I'll test and let you know. Roman.