On Thu, 02 Feb 2023 14:37:08 +0100, Takashi Sakamoto wrote: > > Current structure includes no field to express the number of messages > copied to user space, thus user space application needs to information > out of the structure to parse the content of structure. > > This commit adds a field to express the number of messages copied to user > space since It is more preferable to use self-contained structure. > > Kees Cook proposed an idea of annotation for bound of flexible arrays > in his future improvement for flexible-length array in kernel. The > additional field for message count is suitable to the idea as well. > > Reference: https://people.kernel.org/kees/bounded-flexible-arrays-in-c > Signed-off-by: Takashi Sakamoto <o-takashi@xxxxxxxxxxxxx> Wouldn't changing this break the existing application that talks with the older ABI? Just to be sure... thanks, Takashi > --- > include/uapi/sound/firewire.h | 2 ++ > sound/firewire/fireface/ff-protocol-former.c | 28 +++++++++++--------- > 2 files changed, 18 insertions(+), 12 deletions(-) > > diff --git a/include/uapi/sound/firewire.h b/include/uapi/sound/firewire.h > index 50917581dd2b..1e86872c151f 100644 > --- a/include/uapi/sound/firewire.h > +++ b/include/uapi/sound/firewire.h > @@ -78,6 +78,7 @@ struct snd_firewire_event_motu_register_dsp_change { > * operating hardware knob. > * > * @type: Fixed to SNDRV_FIREWIRE_EVENT_FF400_MESSAGE. > + * @message_count: The number of messages. > * @messages.message: The messages expressing hardware knob operation. > * @messages.tstamp: The isochronous cycle at which the request subaction of asynchronous > * transaction was sent to deliver the message. It has 16 bit unsigned integer > @@ -89,6 +90,7 @@ struct snd_firewire_event_motu_register_dsp_change { > */ > struct snd_firewire_event_ff400_message { > unsigned int type; > + unsigned int message_count; > struct { > __u32 message; > __u32 tstamp; > diff --git a/sound/firewire/fireface/ff-protocol-former.c b/sound/firewire/fireface/ff-protocol-former.c > index fa41de978756..efd59e9d9935 100644 > --- a/sound/firewire/fireface/ff-protocol-former.c > +++ b/sound/firewire/fireface/ff-protocol-former.c > @@ -677,23 +677,19 @@ static void ff400_handle_msg(struct snd_ff *ff, unsigned int offset, const __le3 > > static long ff400_copy_msg_to_user(struct snd_ff *ff, char __user *buf, long count) > { > + struct snd_firewire_event_ff400_message ev = { > + .type = SNDRV_FIREWIRE_EVENT_FF400_MESSAGE, > + .message_count = 0, > + }; > struct ff400_msg_parser *parser = ff->msg_parser; > - u32 type = SNDRV_FIREWIRE_EVENT_FF400_MESSAGE; > long consumed = 0; > - int ret = 0; > + long ret = 0; > > - if (count < 8) > + if (count < sizeof(ev) || parser->pull_pos == parser->push_pos) > return 0; > > - spin_unlock_irq(&ff->lock); > - if (copy_to_user(buf, &type, sizeof(type))) > - ret = -EFAULT; > - spin_lock_irq(&ff->lock); > - if (ret) > - return ret; > - > - count -= sizeof(type); > - consumed += sizeof(type); > + count -= sizeof(ev); > + consumed += sizeof(ev); > > while (count >= sizeof(*parser->msgs) && parser->pull_pos != parser->push_pos) { > spin_unlock_irq(&ff->lock); > @@ -707,10 +703,18 @@ static long ff400_copy_msg_to_user(struct snd_ff *ff, char __user *buf, long cou > ++parser->pull_pos; > if (parser->pull_pos >= FF400_QUEUE_SIZE) > parser->pull_pos = 0; > + ++ev.message_count; > count -= sizeof(*parser->msgs); > consumed += sizeof(*parser->msgs); > } > > + spin_unlock_irq(&ff->lock); > + if (copy_to_user(buf, &ev, sizeof(ev))) > + ret = -EFAULT; > + spin_lock_irq(&ff->lock); > + if (ret) > + return ret; > + > return consumed; > } > > -- > 2.37.2 >
