于 2012年12月04日 00:03, Paul Fulghum 写道:
> On 12/2/2012 8:20 PM, Chen Gang wrote:
>> pardon (I am just learning)
>> does 65535 mean HDLC_MAX_FRAME_SIZE ?
>> why do we need info->max_frame_size >= 4096 ?
>> in drivers/tty/synclink_gt.c:
>> 3550 if (info->max_frame_size < 4096)
>> 3551 info->max_frame_size = 4096;
>> 3552 else if (info->max_frame_size > 65535)
>> 3553 info->max_frame_size = 65535;
>> 3554
>> ...
>> 3603 info->max_frame_size = 4096;
>
> The hardware can send and receive HDLC frames up to
> 64K in size. The driver defaults to 4K max frame size
> to save buffer space for the common case
> (line 3603 in alloc_dev()).
>
> The module parameter max_frame_size can override the default
> in add_device() (lines 3550-3554 are from add_device()
> range checking the module parameter)
>
thank you.
sorry for reply late (yesterday, I have an annual leave for personal things,
and not connect net).
by the way:
does it also need check the length in function rx_get_buf ?
(it seems not, but I am not quite sure, can you give a confirm ?)
4779 /*
4780 * pass receive buffer (RAW synchronous mode) to tty layer
4781 * return true if buffer available, otherwise false
4782 */
4783 static bool rx_get_buf(struct slgt_info *info)
4784 {
4785 unsigned int i = info->rbuf_current;
4786 unsigned int count;
4787
4788 if (!desc_complete(info->rbufs[i]))
4789 return false;
4790 count = desc_count(info->rbufs[i]);
4791 switch(info->params.mode) {
4792 case MGSL_MODE_MONOSYNC:
4793 case MGSL_MODE_BISYNC:
4794 case MGSL_MODE_XSYNC:
4795 /* ignore residue in byte synchronous modes */
4796 if (desc_residue(info->rbufs[i]))
4797 count--;
4798 break;
4799 }
4800 DBGDATA(info, info->rbufs[i].buf, count, "rx");
4801 DBGINFO(("rx_get_buf size=%d\n", count));
4802 if (count)
4803 ldisc_receive_buf(info->port.tty, info->rbufs[i].buf,
4804 info->flag_buf, count);
4805 free_rbufs(info, i, i);
4806 return true;
4807 }
--
Chen Gang
Asianux Corporation
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