"Jacky.S.Mu" <jackyser...@gmail.com> ha scritto:
Hello,
Maybe there is misunderstanding for me while reading the code
freerunner/froyo/hardware/ril/vchanneld.c when I port it to my current
device.
static int vch_write_data(struct virtual_channel *vch, char *ptr, int
len)
{
int tmp;
struct phy_device *phy = vch->phy;
tmp = (len > phy->max_length) ? phy->max_length : len;
while (len > 0) {
gsm0710_write(vch, GSM0710_DATA, ptr,
tmp); // ???????????????????????
ptr += tmp;
len -= tmp;
}
return len;
Yes. It's wrong, post a patch or I will do it.
Michael
}
I am worried the above line tagged with "???..." by me.
In my understanding, the code in the "while" segment is trying to
divide the data to fit the max length requirement. e.g. In freerunner
froyo the "phy->max_length" is set to 128. So if the data length is
greater than 128, it will try to send 128 length of data first and
then the problem seems to appear. It still try to send the 128 length
of data even it is not achieve to the length. And look at the inside
of "gsm0710_write()" and "compute_frame_mux_basic()" this is called by
"gsm0710_write()"
static int compute_frame_mux_basic(struct virtual_channel *vch, int
type,
char *src, int len, char *dst)
{
int hsize, size;
int channel = vch->channel;
dst[0] = (char)GSM0710_FRAME_FLAG;
dst[1] = (char)((channel << 2) | 0x03);
dst[2] = (char)type;
hsize = size = 4;
if (len <= 127) {
dst[3] = (char)((len << 1) | 0x01);
} else {
dst[3] = (char)(len << 1);
dst[4] = (char)(len >> 7);
hsize++;
size++;
}
if (len > 0) {
memcpy(dst + size, src,
len); // ???????????????????????????????????
size += len;
}
dst[size++] = (char)compute_crc((unsigned char *)(dst + 1),
hsize - 1);
dst[size++] = (char)GSM0710_FRAME_FLAG;
return size;
}
Since the last argument 'len' is not accurate and can be greater than
it should be. Is there a chance that it is over the boundary of the
'src', which might results in unexpected consequence?
I also would like to know why the max_length is set to 128 rather than
127 in the freerunner froyo because I saw 127 is the boundary of the
modem to splite the data.
However, my understanding may be wrong. Could anyone correct me or
help me to figure it out?
(If I post to a wrong place, please tell me.)
Thanks
Jack.S
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