[Qemu-devel] Re: [PATCH 5/5] atapi: Implement 'media' subcommand of GET_EVENT_STATUS_NOTIFICATION command

[Amit Shah <amit.shah@redhat.com>]

On (Fri) 08 Apr 2011 [18:17:38], Kevin Wolf wrote:
> Am 08.04.2011 09:15, schrieb Amit Shah:
> > Implement the 'media' sub-command of the GET_EVENT_STATUS_NOTIFICATION
> > command.  This helps us report tray open, tray closed, no media, media
> > present states to the guest.
> > 
> > Newer Linux kernels (2.6.38+) rely on this command to revalidate discs
> > after media change.
> > 
> > This patch also sends out tray open/closed status to the guest driver
> > when requested e.g. via the CDROM_DRIVE_STATUS ioctl (thanks Markus).
> > Without such notification, the guest and qemu's tray open/close status
> > was frequently out of sync, causing installers like Anaconda detecting
> > no disc instead of tray open, confusing them terribly.
> > 
> > Signed-off-by: Amit Shah <amit.shah@redhat.com>
> > ---
> >  hw/ide/core.c     |   93 +++++++++++++++++++++++++++++++++++++++++++++++++++-
> >  hw/ide/internal.h |    6 +++
> >  2 files changed, 97 insertions(+), 2 deletions(-)
> > 
> > diff --git a/hw/ide/core.c b/hw/ide/core.c
> > index cdc2c56..627b2cf 100644
> > --- a/hw/ide/core.c
> > +++ b/hw/ide/core.c
> > @@ -1084,6 +1084,57 @@ static int ide_dvd_read_structure(IDEState *s, int format,
> >      }
> >  }
> >  
> > +static unsigned int event_status_media(IDEState *s,
> > +                                       uint8_t *buf,
> > +                                       unsigned int max_len,
> > +                                       unsigned int event_class,
> > +                                       unsigned int supported_events)
> > +{
> > +    enum media_event_code {
> > +        no_change = 0,       /* Status unchanged */
> > +        eject_requested,     /* received a request from user to eject */
> > +        new_media,           /* new media inserted and ready for access */
> > +        media_removal,       /* only for media changers */
> > +        media_changed,       /* only for media changers */
> > +        bg_format_completed, /* MRW or DVD+RW b/g format completed */
> > +        bg_format_restarted, /* MRW or DVD+RW b/g format restarted */
> > +    };
> > +    enum media_status {
> > +        tray_open = 1,
> > +        media_present = 2,
> > +    };
> > +    uint8_t event_code, media_status;
> > +
> > +    if (max_len < 6) {
> > +        /* We're going to use 6 bytes; don't report anything if we have less */
> > +        return 0;
> > +    }
> 
> Why? Shouldn't we report the first few bytes?

This shouldn't be necessary at all now, isn't it?

> > +
> > +    /* Event notification header */
> > +    cpu_to_ube16(buf, max_len);
> > +    buf[2] = event_class;
> > +    buf[3] = supported_events;
> 
> This should be done in handle_get_event_status_notification as it's not
> specific for media events.

Yes, I moved it here just before the submission.  With the used_len
stuff not being needed anymore, this can be put back there and code
won't look too ugly.

> > +    media_status = 0;
> > +    if (s->bs->tray_open) {
> > +        media_status = tray_open;
> > +    } else if (bdrv_is_inserted(s->bs)) {
> > +        media_status = media_present;
> > +    }
> > +
> > +    /* Event notification descriptor */
> > +    event_code = no_change;
> > +    if (media_status != tray_open && s->events.new_media) {
> > +        event_code = new_media;
> > +        s->events.new_media = false;
> > +    }
> > +
> > +    buf[4] = event_code;
> > +    buf[5] = media_status;
> > +
> > +    return 6; /* We wrote to just 2 extra bytes from the header */
> 
> After media_state, there are two more fields for start/end slot (even
> though they are reserved because we don't have a multiple slot device)

Yes, they're reserved, so we shouldn't change them.  Any change might
trigger bad response from guests.

> So I think we should return 8 and possible zero bytes 6 and 7.
> 
> > +}
> > +
> >  static unsigned int event_status_nea(uint8_t *buf, unsigned int max_len)
> >  {
> >      unsigned int used_len;
> > @@ -1125,7 +1176,28 @@ static void handle_get_event_status_notification(IDEState *s,
> >          allocation_length_lsb = 8,
> >          control = 9,
> >      };
> > +    enum notification_class_request_type {
> > +        reserved1 = 1 << 0,
> > +        operational_change = 1 << 1,
> > +        power_management = 1 << 2,
> > +        external_request = 1 << 3,
> > +        media = 1 << 4,
> > +        multi_host = 1 << 5,
> > +        device_busy = 1 << 6,
> > +        reserved2 = 1 << 7,
> > +    };
> > +    enum event_notification_class_field {
> > +        enc_no_events = 0,
> > +        enc_operational_change,
> > +        enc_power_management,
> > +        enc_external_request,
> > +        enc_media,
> > +        enc_multiple_hosts,
> > +        enc_device_busy,
> > +        enc_reserved,
> > +    };
> >      unsigned int max_len, used_len;
> > +    unsigned int supported_events;
> >  
> >      max_len = ube16_to_cpu(packet + allocation_length_msb);
> >  
> > @@ -1139,8 +1211,24 @@ static void handle_get_event_status_notification(IDEState *s,
> >  
> >      /* polling mode operation */
> >  
> > -    /* We don't support any event class (yet). */
> > -    used_len = event_status_nea(buf, max_len);
> > +    /*
> > +     * These are the supported events.
> > +     *
> > +     * We currently only support requests of the 'media' type.
> > +     */
> > +    supported_events = media;
> > +
> > +    /*
> > +     * Responses to requests are to be based on request priority.  The
> > +     * notification_class_request_type enum above specifies the
> > +     * priority: upper elements are higher prio than lower ones.
> > +     */
> > +    if (packet[request] & media) {
> > +        used_len = event_status_media(s, buf, max_len, enc_media,
> > +                                      supported_events);
> > +    } else {
> > +        used_len = event_status_nea(buf, max_len);
> > +    }
> 
> Once you put the event header here, there's no need for event_status_nea
> any more because it just mean not adding any descriptors. That will work
> much better as soon as we have more even classes, too.

Hm, I didn't do it that way when I first coded this so there must've
been something that I'm forgetting now.

> 
> >      ide_atapi_cmd_reply(s, used_len, max_len);
> >  }
> >  
> > @@ -1661,6 +1749,7 @@ static void cdrom_change_cb(void *opaque, int reason)
> >      s->sense_key = SENSE_UNIT_ATTENTION;
> >      s->asc = ASC_MEDIUM_MAY_HAVE_CHANGED;
> >      s->cdrom_changed = 1;
> > +    s->events.new_media = true;
> >      ide_set_irq(s->bus);
> >  }
> >  
> > diff --git a/hw/ide/internal.h b/hw/ide/internal.h
> > index d533fb6..ba7e9a8 100644
> > --- a/hw/ide/internal.h
> > +++ b/hw/ide/internal.h
> > @@ -373,6 +373,11 @@ typedef int DMAFunc(IDEDMA *);
> >  typedef int DMAIntFunc(IDEDMA *, int);
> >  typedef void DMARestartFunc(void *, int, int);
> >  
> > +struct unreported_events {
> > +    bool eject_request;
> > +    bool new_media;
> > +};
> > +
> >  /* NOTE: IDEState represents in fact one drive */
> >  struct IDEState {
> >      IDEBus *bus;
> > @@ -408,6 +413,7 @@ struct IDEState {
> >      BlockDriverState *bs;
> >      char version[9];
> >      /* ATAPI specific */
> > +    struct unreported_events events;
> >      uint8_t sense_key;
> >      uint8_t asc;
> >      uint8_t cdrom_changed;
> 
> Do we need to add some vmstate fields?

Yes!  I had it in mind till sometime back.

		Amit