Re: [Qemu-devel] [PATCH v4 5/5] atapi: GESN: implement 'media' subcommand

[Kevin Wolf <kwolf@redhat.com>]

Am 12.04.2011 17:03, schrieb Amit Shah:
> On (Tue) 12 Apr 2011 [16:54:53], Kevin Wolf wrote:
>> Am 12.04.2011 16:09, 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     |  109 ++++++++++++++++++++++++++++++++++++++++++++++++++--
>>>  hw/ide/internal.h |    6 +++
>>>  2 files changed, 110 insertions(+), 5 deletions(-)
>>>
>>> diff --git a/hw/ide/core.c b/hw/ide/core.c
>>> index dafc049..209d8e6 100644
>>> --- a/hw/ide/core.c
>>> +++ b/hw/ide/core.c
>>> @@ -1084,6 +1084,49 @@ 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)
>>> +{
>>> +    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;
>>> +
>>> +    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;
>>> +
>>> +    /* These fields are reserved, just clear them. */
>>> +    buf[6] = 0;
>>> +    buf[7] = 0;
>>> +
>>> +    return 8; /* We wrote to 4 extra bytes from the header */
>>> +}
>>> +
>>>  static void handle_get_event_status_notification(IDEState *s,
>>>                                                   uint8_t *buf,
>>>                                                   const uint8_t *packet)
>>> @@ -1104,6 +1147,26 @@ static void handle_get_event_status_notification(IDEState *s,
>>>          uint8_t supported_events;
>>>      } __attribute((packed)) *gesn_event_header;
>>>  
>>> +    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;
>>>  
>>>      gesn_cdb = (void *)packet;
>>> @@ -1121,12 +1184,25 @@ static void handle_get_event_status_notification(IDEState *s,
>>>  
>>>      /* polling mode operation */
>>>  
>>> -    /* We don't support any event class (yet). */
>>> -    gesn_event_header->supported_events = 0;
>>> -
>>> -    gesn_event_header->notification_class = 0x80; /* No event available */
>>> -    used_len = sizeof(*gesn_event_header);
>>> +    /*
>>> +     * These are the supported events.
>>> +     *
>>> +     * We currently only support requests of the 'media' type.
>>> +     */
>>> +    gesn_event_header->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 (gesn_cdb->class & media) {
>>> +        gesn_event_header->notification_class |= enc_media;
>>
>> Am I missing where this field is initialized or should it be = instead
>> of |= ?
> 
> I considered both: if the 'reserved' bits become available and if we
> should write to them, |= makes more sense.  Currently, = will
> suffice.  Strong preference?

|= is fine if the field is initialized to 0 and you add flags to it. But
this patch seems to remove the zero initialization. Maybe it's still
there somewhere, I just don't see it right now.

Kevin