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iichid: Stop using split I²C bus transactions

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Read IIC-HID reports as a single I²C transaction, instead of reading
first the two byte length field, holding the bus, and then the rest
of the report in a separate transaction.

While technically legal, I²C bus split transactions are not universally
supported, and in particular the "Snapdragon Elite" ARM CPU does
not seem to support them.

It is also not obvious that they are beneficial in this case, given
the overhead of controller setup, interrupts and tear-down.

Reviewed by: wulf
Differential Revision: https://reviews.freebsd.org/D51302
This commit is contained in:
Poul-Henning Kamp 2025-07-29 06:17:43 +00:00
parent 659962f96a
commit 36027361f9
1 changed files with 27 additions and 47 deletions
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74
sys/dev/iicbus/iichid.c
View file

@ -275,62 +275,36 @@ iichid_cmd_read(struct iichid_softc* sc, void *buf, iichid_size_t maxlen,
* 6.1.3 - Retrieval of Input Reports
* DEVICE returns the length (2 Bytes) and the entire Input Report.
*/
uint8_t actbuf[2] = { 0, 0 };
/* Read actual input report length. */
memset(buf, 0xaa, 2); // In case nothing gets read
struct iic_msg msgs[] = {
{ sc->addr, IIC_M_RD | IIC_M_NOSTOP, sizeof(actbuf), actbuf },
{ sc->addr, IIC_M_RD, maxlen, buf },
};
uint16_t actlen;
int error;
error = iicbus_transfer(sc->dev, msgs, nitems(msgs));
if (error != 0)
return (error);
actlen = actbuf[0] | actbuf[1] << 8;
#ifdef IICHID_SAMPLING
if ((actlen == 0 && sc->sampling_rate_slow < 0) ||
(maxlen == 0 && sc->sampling_rate_slow >= 0)) {
#else
DPRINTFN(sc, 5, "%*D\n", msgs[0].len, msgs[0].buf, " ");
uint16_t actlen = le16dec(buf);
if (actlen == 0) {
#endif
/* Read and discard reset command response. */
msgs[0] = (struct iic_msg)
{ sc->addr, IIC_M_RD | IIC_M_NOSTART,
le16toh(sc->desc.wMaxInputLength) - 2, sc->intr_buf };
actlen = 0;
if (!sc->reset_acked) {
mtx_lock(&sc->mtx);
sc->reset_acked = true;
wakeup(&sc->reset_acked);
mtx_unlock(&sc->mtx);
}
#ifdef IICHID_SAMPLING
} else if ((actlen <= 2 || actlen == 0xFFFF) &&
sc->sampling_rate_slow >= 0) {
/* Read and discard 1 byte to send I2C STOP condition. */
msgs[0] = (struct iic_msg)
{ sc->addr, IIC_M_RD | IIC_M_NOSTART, 1, actbuf };
actlen = 0;
#endif
} else {
actlen -= 2;
if (actlen > maxlen) {
DPRINTF(sc, "input report too big. requested=%d "
"received=%d\n", maxlen, actlen);
actlen = maxlen;
}
/* Read input report itself. */
msgs[0] = (struct iic_msg)
{ sc->addr, IIC_M_RD | IIC_M_NOSTART, actlen, buf };
}
error = iicbus_transfer(sc->dev, msgs, 1);
if (error == 0 && actual_len != NULL)
if (actlen <= 2 || actlen > maxlen) {
actlen = 0;
}
if (actual_len != NULL) {
*actual_len = actlen;
DPRINTFN(sc, 5,
"%*D - %*D\n", 2, actbuf, " ", msgs[0].len, msgs[0].buf, " ");
}
return (error);
}
@ -566,7 +540,7 @@ iichid_sampling_task(void *context, int pending)
error = iichid_cmd_read(sc, sc->intr_buf, sc->intr_bufsize, &actual);
if (error == 0) {
if (actual > 0) {
sc->intr_handler(sc->intr_ctx, sc->intr_buf, actual);
sc->intr_handler(sc->intr_ctx, sc->intr_buf + 2, actual);
sc->missing_samples = 0;
if (sc->dup_size != actual ||
memcmp(sc->dup_buf, sc->intr_buf, actual) != 0) {
@ -577,7 +551,7 @@ iichid_sampling_task(void *context, int pending)
++sc->dup_samples;
} else {
if (++sc->missing_samples == 1)
sc->intr_handler(sc->intr_ctx, sc->intr_buf, 0);
sc->intr_handler(sc->intr_ctx, sc->intr_buf + 2, 0);
sc->dup_samples = 0;
}
} else
@ -632,7 +606,7 @@ iichid_intr(void *context)
if (error == 0) {
if (sc->power_on && sc->open) {
if (actual != 0)
sc->intr_handler(sc->intr_ctx, sc->intr_buf,
sc->intr_handler(sc->intr_ctx, sc->intr_buf + 2,
actual);
else
DPRINTF(sc, "no data received\n");
@ -842,11 +816,12 @@ iichid_intr_setup(device_t dev, device_t child __unused, hid_intr_t intr,
sc = device_get_softc(dev);
/*
* Do not rely on wMaxInputLength, as some devices may set it to
* a wrong length. Find the longest input report in report descriptor.
* Do not rely just on wMaxInputLength, as some devices (which?)
* may set it to a wrong length. Also find the longest input report
* in report descriptor, and add two for the length field.
*/
rdesc->rdsize =
MAX(rdesc->isize, le16toh(sc->desc.wMaxInputLength) - 2);
rdesc->rdsize = 2 +
MAX(rdesc->isize, le16toh(sc->desc.wMaxInputLength));
/* Write and get/set_report sizes are limited by I2C-HID protocol. */
rdesc->grsize = rdesc->srsize = IICHID_SIZE_MAX;
rdesc->wrsize = IICHID_SIZE_MAX;
@ -919,7 +894,7 @@ iichid_intr_poll(device_t dev, device_t child __unused)
sc = device_get_softc(dev);
error = iichid_cmd_read(sc, sc->intr_buf, sc->intr_bufsize, &actual);
if (error == 0 && actual != 0)
sc->intr_handler(sc->intr_ctx, sc->intr_buf, actual);
sc->intr_handler(sc->intr_ctx, sc->intr_buf + 2, actual);
}
/*
@ -946,6 +921,7 @@ iichid_read(device_t dev, device_t child __unused, void *buf,
{
struct iichid_softc *sc;
device_t parent;
uint8_t *tmpbuf;
int error;
if (maxlen > IICHID_SIZE_MAX)
@ -954,8 +930,12 @@ iichid_read(device_t dev, device_t child __unused, void *buf,
parent = device_get_parent(sc->dev);
error = iicbus_request_bus(parent, sc->dev, IIC_WAIT);
if (error == 0) {
error = iichid_cmd_read(sc, buf, maxlen, actlen);
tmpbuf = malloc(maxlen + 2, M_DEVBUF, M_WAITOK | M_ZERO);
error = iichid_cmd_read(sc, tmpbuf, maxlen + 2, actlen);
iicbus_release_bus(parent, sc->dev);
if (*actlen > 0)
memcpy(buf, tmpbuf + 2, *actlen);
free(tmpbuf, M_DEVBUF);
}
return (iic2errno(error));
}