From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:51159) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XSqhI-00036A-8t for qemu-devel@nongnu.org; Sat, 13 Sep 2014 13:01:22 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1XSqh9-0006Cr-U7 for qemu-devel@nongnu.org; Sat, 13 Sep 2014 13:01:16 -0400 Received: from mx1.redhat.com ([209.132.183.28]:53242) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XSqh9-0006CW-Mh for qemu-devel@nongnu.org; Sat, 13 Sep 2014 13:01:07 -0400 Received: from int-mx10.intmail.prod.int.phx2.redhat.com (int-mx10.intmail.prod.int.phx2.redhat.com [10.5.11.23]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id s8DH16mD022637 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL) for ; Sat, 13 Sep 2014 13:01:06 -0400 Message-ID: <5414784D.6060308@redhat.com> Date: Sat, 13 Sep 2014 13:01:01 -0400 From: John Snow MIME-Version: 1.0 References: <1410582855-21870-1-git-send-email-jsnow@redhat.com> <1410582855-21870-2-git-send-email-jsnow@redhat.com> <54143E8D.3010704@redhat.com> In-Reply-To: <54143E8D.3010704@redhat.com> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [RFC 01/10] ide: add is_write() macro for semantic consistency List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Paolo Bonzini , qemu-devel@nongnu.org Cc: stefanha@redhat.com, mst@redhat.com On 09/13/2014 08:54 AM, Paolo Bonzini wrote: > Il 13/09/2014 06:34, John Snow ha scritto: >> The prepare_buf callback takes an argument named /is_write/, >> however in core.c we are checking to see if this DMA command >> is /is_read/. I am adding a small macro to correct this oversight. >> >> Impact: Nothing, yet. >> -The prepare_buf callback is only used in ahci and pci, and both >> versions of this callback name the incoming argument is_write. >> -Both functions ignore this hint currently, anyway. >> >> This is therefore a simple patch to avoid future mistakes. >> >> Signed-off-by: John Snow >> --- >> hw/ide/core.c | 2 +- >> hw/ide/internal.h | 2 ++ >> 2 files changed, 3 insertions(+), 1 deletion(-) >> >> diff --git a/hw/ide/core.c b/hw/ide/core.c >> index 191f893..3d682e2 100644 >> --- a/hw/ide/core.c >> +++ b/hw/ide/core.c >> @@ -718,7 +718,7 @@ void ide_dma_cb(void *opaque, int ret) >> n = s->nsector; >> s->io_buffer_index = 0; >> s->io_buffer_size = n * 512; >> - if (s->bus->dma->ops->prepare_buf(s->bus->dma, ide_cmd_is_read(s)) == 0) { >> + if (s->bus->dma->ops->prepare_buf(s->bus->dma, ide_cmd_is_write(s)) == 0) { >> /* The PRDs were too short. Reset the Active bit, but don't raise an >> * interrupt. */ >> s->status = READY_STAT | SEEK_STAT; >> diff --git a/hw/ide/internal.h b/hw/ide/internal.h >> index 5c19f79..72d0147 100644 >> --- a/hw/ide/internal.h >> +++ b/hw/ide/internal.h >> @@ -338,6 +338,8 @@ enum ide_dma_cmd { >> >> #define ide_cmd_is_read(s) \ >> ((s)->dma_cmd == IDE_DMA_READ) >> +#define ide_cmd_is_write(s) \ >> + ((s)->dma_cmd == IDE_DMA_WRITE) >> >> /* NOTE: IDEState represents in fact one drive */ >> struct IDEState { >> > > Actually the code is right (!). > > A read command corresponds to a DMA write. A write or trim will read > data from memory, so it is a DMA read. > > See for example how rw_buf is only used from the READ CD command, but > passes 1 for the second argument of prepare_buf. > > Paolo > Ah, okay ... It didn't seem as if this argument was actually getting /used/ anywhere yet, so it wasn't really clear what it was intended to mean or for whom. None of the prepare_buf implementations actually seem to use this bit. If you think this is correct the way it is, we should probably add some documentation to the prepare_buf callback to explain the nature of the argument to prevent someone from being helpful and trying to fix it again in the future. Thanks for reviewing, this series is RFC for a reason :)