Re: [PATCH 05/26] cinergyT2-fe: don't do DMA on stack

From: Patrick Boettcher
Date: Mon Oct 10 2016 - 02:39:25 EST


On Fri, 7 Oct 2016 14:24:15 -0300
Mauro Carvalho Chehab <mchehab@xxxxxxxxxxxxxxxx> wrote:

> The USB control messages require DMA to work. We cannot pass
> a stack-allocated buffer, as it is not warranted that the
> stack would be into a DMA enabled area.
>
> Signed-off-by: Mauro Carvalho Chehab <mchehab@xxxxxxxxxxxxxxxx>
> ---
> drivers/media/usb/dvb-usb/cinergyT2-fe.c | 45
> ++++++++++++++++---------------- 1 file changed, 23 insertions(+), 22
> deletions(-)
>
> diff --git a/drivers/media/usb/dvb-usb/cinergyT2-fe.c
> b/drivers/media/usb/dvb-usb/cinergyT2-fe.c index
> fd8edcb56e61..03ba66ef1f28 100644 ---
> a/drivers/media/usb/dvb-usb/cinergyT2-fe.c +++
> b/drivers/media/usb/dvb-usb/cinergyT2-fe.c @@ -139,6 +139,9 @@ static
> uint16_t compute_tps(struct dtv_frontend_properties *op) struct
> cinergyt2_fe_state { struct dvb_frontend fe;
> struct dvb_usb_device *d;
> +
> + unsigned char data[64];
> +
> struct dvbt_get_status_msg status;
> };
>
> @@ -146,28 +149,28 @@ static int cinergyt2_fe_read_status(struct
> dvb_frontend *fe, enum fe_status *status)
> {
> struct cinergyt2_fe_state *state = fe->demodulator_priv;
> - struct dvbt_get_status_msg result;
> - u8 cmd[] = { CINERGYT2_EP1_GET_TUNER_STATUS };
> int ret;
>
> - ret = dvb_usb_generic_rw(state->d, cmd, sizeof(cmd), (u8
> *)&result,
> - sizeof(result), 0);
> + state->data[0] = CINERGYT2_EP1_GET_TUNER_STATUS;
> +
> + ret = dvb_usb_generic_rw(state->d, state->data, 1,
> + state->data, sizeof(state->status),
> 0); if (ret < 0)
> return ret;
>
> - state->status = result;
> + memcpy(&state->status, state->data, sizeof(state->status));
>
> *status = 0;
>
> - if (0xffff - le16_to_cpu(result.gain) > 30)
> + if (0xffff - le16_to_cpu(state->status.gain) > 30)
> *status |= FE_HAS_SIGNAL;
> - if (result.lock_bits & (1 << 6))
> + if (state->status.lock_bits & (1 << 6))
> *status |= FE_HAS_LOCK;
> - if (result.lock_bits & (1 << 5))
> + if (state->status.lock_bits & (1 << 5))
> *status |= FE_HAS_SYNC;
> - if (result.lock_bits & (1 << 4))
> + if (state->status.lock_bits & (1 << 4))
> *status |= FE_HAS_CARRIER;
> - if (result.lock_bits & (1 << 1))
> + if (state->status.lock_bits & (1 << 1))
> *status |= FE_HAS_VITERBI;
>
> if ((*status & (FE_HAS_CARRIER | FE_HAS_VITERBI |
> FE_HAS_SYNC)) != @@ -232,31 +235,29 @@ static int
> cinergyt2_fe_set_frontend(struct dvb_frontend *fe) {
> struct dtv_frontend_properties *fep =
> &fe->dtv_property_cache; struct cinergyt2_fe_state *state =
> fe->demodulator_priv;
> - struct dvbt_set_parameters_msg param;
> - char result[2];
> + struct dvbt_set_parameters_msg *param = (void *)state->data;
> int err;
>
> - param.cmd = CINERGYT2_EP1_SET_TUNER_PARAMETERS;
> - param.tps = cpu_to_le16(compute_tps(fep));
> - param.freq = cpu_to_le32(fep->frequency / 1000);
> - param.flags = 0;
> + param->cmd = CINERGYT2_EP1_SET_TUNER_PARAMETERS;
> + param->tps = cpu_to_le16(compute_tps(fep));
> + param->freq = cpu_to_le32(fep->frequency / 1000);
> + param->flags = 0;
>
> switch (fep->bandwidth_hz) {
> default:
> case 8000000:
> - param.bandwidth = 8;
> + param->bandwidth = 8;
> break;
> case 7000000:
> - param.bandwidth = 7;
> + param->bandwidth = 7;
> break;
> case 6000000:
> - param.bandwidth = 6;
> + param->bandwidth = 6;
> break;
> }
>
> - err = dvb_usb_generic_rw(state->d,
> - (char *)&param, sizeof(param),
> - result, sizeof(result), 0);
> + err = dvb_usb_generic_rw(state->d, state->data,
> sizeof(*param),
> + state->data, 2, 0);
> if (err < 0)
> err("cinergyt2_fe_set_frontend() Failed! err=%d\n",
> err);

Reviewed-By: Patrick Boettcher <patrick.boettcher@xxxxxxxxx>