Re: [Qemu-block] [Qemu-devel] [PATCH] block.c: fix real cdrom detection

[Programmingkid]

On Jun 28, 2015, at 8:29 PM, Laurent Vivier wrote:

Hi,

On 29/06/2015 01:43, Programmingkid wrote:

On Jun 25, 2015, at 2:01 PM, Peter Maydell wrote:

On 25 June 2015 at 18:56, Programmingkid

<address@hidden> wrote:

Nice to hear from you again Laurent. The only way a solution in

hdev_open() would work is if it could prevent

find_image_format() from executing. Otherwise find_image_format()

would just quit QEMU with an error.

The question you should be asking is "what is Linux doing for raw

CDROM devices that is different, such that it works there but

doesn't work on OSX?".

It would also be helpful to know which is the case that doesn't

work. Does QEMU fail in all cases, or only if the cdrom drive is

empty, or only if there's a disk in the drive?

QEMU fails if the cdrom is specified "-cdrom /dev/cdrom", and there

is no cd in the drive.

QEMU also fails with a real cdrom in the drive.

My initial suspicion is that we need OSX support in raw-posix.c for

handling the host CDROM specially -- note that Linux and FreeBSD

register a bdrv_host_cdrom with an is_inserted function.

The is_inserted function wouldn't make a difference.

In fact, if your patch fixes the problem, the is_inserted with no
cdrom should too:

with your " strcmp("/dev/cdrom", filename) == 0 ", you force the
selection of bdrv_raw (which is what to do).

without your patch, if "bdrv_is_inserted()" was implemented and no cdrom
in the drive " !bdrv_is_inserted(bs)  " should also select bdrv_raw.

It appears also that bdrv_host_cdrom is not registered in
bdrv_file_init(). I think this is the missing part to have a host cdrom
support on MacOS X.

Laurent

This patch is what I came up with using your idea. It uses the fact that the bdrv_is_inserted() function is called first from find_image_format(). The bdrv_is_inserted() function now points to cdrom_is_inserted(). This new function will return 0 the first time it is called, then 1 after that. So far it works.

---

 block/raw-posix.c |   21 +++++++++++++++++++++

 1 files changed, 21 insertions(+), 0 deletions(-)

diff --git a/block/raw-posix.c b/block/raw-posix.c

index a967464..2d35580 100644

--- a/block/raw-posix.c

+++ b/block/raw-posix.c

@@ -2324,6 +2324,23 @@ static int hdev_create(const char *filename, QemuOpts *opts,

     return ret;

 }

 

+#ifdef __APPLE__

+

+static int cdrom_is_inserted(BlockDriverState *bs)

+{

+    static int count = 0;

+    int returnValue = 1;

+    

+    if(count == 0) {

+        returnValue = 0; // get around find_image_format() issue

+    }

+    

+    printf("count = %d for %s, returning %d\n", count, bs->filename, returnValue);

+    count++;

+    return returnValue;

+}

+#endif

+

 static BlockDriver bdrv_host_device = {

     .format_name        = "host_device",

     .protocol_name        = "host_device",

@@ -2365,6 +2382,10 @@ static BlockDriver bdrv_host_device = {

     .bdrv_ioctl         = hdev_ioctl,

     .bdrv_aio_ioctl     = hdev_aio_ioctl,

 #endif

+

+#ifdef __APPLE__

+    .bdrv_is_inserted   = cdrom_is_inserted,

+#endif

 };

 

 #ifdef __linux__

-- 

1.7.5.4