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Subject[RFC] [DVB][FRONTEND] Added a new ioctl for optimizing frontend property set operation
Date
-For setting one frontend property , one FE_SET_PROPERTY ioctl is called
-Since, size of struct dtv_property is 72 bytes, this ioctl requires
---allocating 72 bytes of memory in user space
---allocating 72 bytes of memory in kernel space
---copying 72 bytes of data from user space to kernel space
-However, for all the properties, only 8 out of 72 bytes are used
for setting the property
-Four bytes are needed for specifying property type and another 4 for
property value
-Moreover, there are 2 properties DTV_CLEAR and DTV_TUNE which use
only 4 bytes for property name
---They don't use property value
-Therefore, we have defined new short variant/forms/version of currently
used structures for such 8 byte properties.
-This results in 89% (8*100/72) of memory saving in user and kernel space
each.
-This also results in faster copy (8 bytes as compared to 72 bytes) from
user to kernel space
-We have added new ioctl FE_SET_PROPERTY_SHORT which utilizes above
mentioned new property structures
-This ioctl can co-exist with present ioctl FE_SET_PROPERTY
-If the apps wish to use shorter forms they can use
proposed FE_SET_PROPERTY_SHORT, rest of them can continue to use
current versions FE_SET_PROPERTY
-We are currently not validating incoming properties in
function dtv_property_short_process_set because most of
the frontend drivers in linux source are not using the
method ops.set_property. Just two drivers are using it
drivers/media/dvb-frontends/stv0288.c
driver/media/usb/dvb-usb/friio-fe.c
-Moreover, stv0288 driver implemments blank function
for set_property.
-If needed in future, we can define a new
ops.set_property_short method to support
struct dtv_property_short.
Signed-off-by: Satendra Singh Thakur <satendra.t@samsung.com>
---
drivers/media/dvb-core/dvb_frontend.c | 228 +++++++++++++++++++++++++++++++++-
include/uapi/linux/dvb/frontend.h | 24 ++++
2 files changed, 248 insertions(+), 4 deletions(-)

diff --git a/drivers/media/dvb-core/dvb_frontend.c b/drivers/media/dvb-core/dvb_frontend.c
index e3fff8f..e183025 100644
--- a/drivers/media/dvb-core/dvb_frontend.c
+++ b/drivers/media/dvb-core/dvb_frontend.c
@@ -1914,6 +1914,192 @@ static int dtv_property_process_set(struct dvb_frontend *fe,
return r;
}

+/**
+ * dtv_property_short_process_set
+ * @fe: Pointer to struct dvb_frontend
+ * @tvp: Pointer to struct dtv_property_short
+ * @file: Pointer to struct file
+ *
+ * helper function for dvb_frontend_ioctl_properties,
+ * which can be used to set dtv property using ioctl
+ * cmd FE_SET_PROPERTY_SHORT.
+ * It assigns property value to corresponding member of
+ * property-cache structure
+ * This func is a variant of the func dtv_property_process_set
+ * Returns:
+ * Zero on success, negative errno on failure.
+ */
+static int dtv_property_short_process_set(struct dvb_frontend *fe,
+ struct dtv_property_short *tvp,
+ struct file *file)
+{
+ int r = 0;
+ struct dtv_frontend_properties *c = &fe->dtv_property_cache;
+ /* Currently, We do not allow the frontend to validate incoming
+ * properties, currently, just 2 drivers are using
+ * ops.set_property method , If required, we can define new
+ * ops.set_property_short method for this purpose
+ */
+ switch (tvp->cmd) {
+ case DTV_CLEAR:
+ /*
+ * Reset a cache of data specific to the frontend here. This
+ * does not effect hardware.
+ */
+ dvb_frontend_clear_cache(fe);
+ break;
+ case DTV_TUNE:
+ /* interpret the cache of data, build either a traditional
+ * frontend tune request so we can pass validation in the
+ * FE_SET_FRONTEND ioctl.
+ */
+ c->state = tvp->cmd;
+ dev_dbg(fe->dvb->device, "%s: Finalised property cache\n",
+ __func__);
+
+ r = dtv_set_frontend(fe);
+ break;
+ case DTV_FREQUENCY:
+ c->frequency = tvp->data;
+ break;
+ case DTV_MODULATION:
+ c->modulation = tvp->data;
+ break;
+ case DTV_BANDWIDTH_HZ:
+ c->bandwidth_hz = tvp->data;
+ break;
+ case DTV_INVERSION:
+ c->inversion = tvp->data;
+ break;
+ case DTV_SYMBOL_RATE:
+ c->symbol_rate = tvp->data;
+ break;
+ case DTV_INNER_FEC:
+ c->fec_inner = tvp->data;
+ break;
+ case DTV_PILOT:
+ c->pilot = tvp->data;
+ break;
+ case DTV_ROLLOFF:
+ c->rolloff = tvp->data;
+ break;
+ case DTV_DELIVERY_SYSTEM:
+ r = dvbv5_set_delivery_system(fe, tvp->data);
+ break;
+ case DTV_VOLTAGE:
+ c->voltage = tvp->data;
+ r = dvb_frontend_ioctl_legacy(file, FE_SET_VOLTAGE,
+ (void *)c->voltage);
+ break;
+ case DTV_TONE:
+ c->sectone = tvp->data;
+ r = dvb_frontend_ioctl_legacy(file, FE_SET_TONE,
+ (void *)c->sectone);
+ break;
+ case DTV_CODE_RATE_HP:
+ c->code_rate_HP = tvp->data;
+ break;
+ case DTV_CODE_RATE_LP:
+ c->code_rate_LP = tvp->data;
+ break;
+ case DTV_GUARD_INTERVAL:
+ c->guard_interval = tvp->data;
+ break;
+ case DTV_TRANSMISSION_MODE:
+ c->transmission_mode = tvp->data;
+ break;
+ case DTV_HIERARCHY:
+ c->hierarchy = tvp->data;
+ break;
+ case DTV_INTERLEAVING:
+ c->interleaving = tvp->data;
+ break;
+
+ /* ISDB-T Support here */
+ case DTV_ISDBT_PARTIAL_RECEPTION:
+ c->isdbt_partial_reception = tvp->data;
+ break;
+ case DTV_ISDBT_SOUND_BROADCASTING:
+ c->isdbt_sb_mode = tvp->data;
+ break;
+ case DTV_ISDBT_SB_SUBCHANNEL_ID:
+ c->isdbt_sb_subchannel = tvp->data;
+ break;
+ case DTV_ISDBT_SB_SEGMENT_IDX:
+ c->isdbt_sb_segment_idx = tvp->data;
+ break;
+ case DTV_ISDBT_SB_SEGMENT_COUNT:
+ c->isdbt_sb_segment_count = tvp->data;
+ break;
+ case DTV_ISDBT_LAYER_ENABLED:
+ c->isdbt_layer_enabled = tvp->data;
+ break;
+ case DTV_ISDBT_LAYERA_FEC:
+ c->layer[0].fec = tvp->data;
+ break;
+ case DTV_ISDBT_LAYERA_MODULATION:
+ c->layer[0].modulation = tvp->data;
+ break;
+ case DTV_ISDBT_LAYERA_SEGMENT_COUNT:
+ c->layer[0].segment_count = tvp->data;
+ break;
+ case DTV_ISDBT_LAYERA_TIME_INTERLEAVING:
+ c->layer[0].interleaving = tvp->data;
+ break;
+ case DTV_ISDBT_LAYERB_FEC:
+ c->layer[1].fec = tvp->data;
+ break;
+ case DTV_ISDBT_LAYERB_MODULATION:
+ c->layer[1].modulation = tvp->data;
+ break;
+ case DTV_ISDBT_LAYERB_SEGMENT_COUNT:
+ c->layer[1].segment_count = tvp->data;
+ break;
+ case DTV_ISDBT_LAYERB_TIME_INTERLEAVING:
+ c->layer[1].interleaving = tvp->data;
+ break;
+ case DTV_ISDBT_LAYERC_FEC:
+ c->layer[2].fec = tvp->data;
+ break;
+ case DTV_ISDBT_LAYERC_MODULATION:
+ c->layer[2].modulation = tvp->data;
+ break;
+ case DTV_ISDBT_LAYERC_SEGMENT_COUNT:
+ c->layer[2].segment_count = tvp->data;
+ break;
+ case DTV_ISDBT_LAYERC_TIME_INTERLEAVING:
+ c->layer[2].interleaving = tvp->data;
+ break;
+
+ /* Multistream support */
+ case DTV_STREAM_ID:
+ case DTV_DVBT2_PLP_ID_LEGACY:
+ c->stream_id = tvp->data;
+ break;
+
+ /* ATSC-MH */
+ case DTV_ATSCMH_PARADE_ID:
+ fe->dtv_property_cache.atscmh_parade_id = tvp->data;
+ break;
+ case DTV_ATSCMH_RS_FRAME_ENSEMBLE:
+ fe->dtv_property_cache.atscmh_rs_frame_ensemble = tvp->data;
+ break;
+
+ case DTV_LNA:
+ c->lna = tvp->data;
+ if (fe->ops.set_lna)
+ r = fe->ops.set_lna(fe);
+ if (r < 0)
+ c->lna = LNA_AUTO;
+ break;
+
+ default:
+ return -EINVAL;
+ }
+
+ return r;
+}
+
static int dvb_frontend_ioctl(struct file *file,
unsigned int cmd, void *parg)
{
@@ -1939,7 +2125,8 @@ static int dvb_frontend_ioctl(struct file *file,
return -EPERM;
}

- if ((cmd == FE_SET_PROPERTY) || (cmd == FE_GET_PROPERTY))
+ if ((cmd == FE_SET_PROPERTY) || (cmd == FE_GET_PROPERTY)
+ || (cmd == FE_SET_PROPERTY_SHORT))
err = dvb_frontend_ioctl_properties(file, cmd, parg);
else {
c->state = DTV_UNDEFINED;
@@ -2026,9 +2213,42 @@ static int dvb_frontend_ioctl_properties(struct file *file,
err = -EFAULT;
goto out;
}
-
- } else
- err = -EOPNOTSUPP;
+ /* New ioctl for optimizing property set
+ */
+ } else if (cmd == FE_SET_PROPERTY_SHORT) {
+ struct dtv_property_short *tvp_short = NULL;
+ struct dtv_properties_short *tvps_short = parg;
+
+ dev_dbg(fe->dvb->device, "%s: properties.num = %d\n", \
+ __func__, tvps_short->num);
+ dev_dbg(fe->dvb->device, "%s: properties.props = %p\n", \
+ __func__, tvps_short->props);
+ if ((!tvps_short->num) ||
+ (tvps_short->num > DTV_IOCTL_MAX_MSGS))
+ return -EINVAL;
+ tvp_short = memdup_user(tvps_short->props,
+ tvps_short->num * sizeof(*tvp_short));
+ if (IS_ERR(tvp_short))
+ return PTR_ERR(tvp_short);
+ for (i = 0; i < tvps_short->num; i++) {
+ err = dtv_property_short_process_set(fe, tvp_short + i,\
+ file);
+ if (err < 0) {
+ kfree(tvp_short);
+ return err;
+ }
+ /* Since we are returning when error occurs
+ * There is no need to store the result as it
+ * would have been >=0 in case we didn't return
+ * (tvp + i)->result = err;
+ */
+ }
+ if (c->state == DTV_TUNE)
+ dev_dbg(fe->dvb->device, "%s: Property cache\
+ is full, tuning\n", __func__);
+ kfree(tvp_short);
+ } else
+ err = -EOPNOTSUPP;

out:
kfree(tvp);
diff --git a/include/uapi/linux/dvb/frontend.h b/include/uapi/linux/dvb/frontend.h
index 00a20cd..aa82179 100644
--- a/include/uapi/linux/dvb/frontend.h
+++ b/include/uapi/linux/dvb/frontend.h
@@ -476,6 +476,17 @@ struct dtv_property {
int result;
} __attribute__ ((packed));

+/**
+ * @struct dtv_property_short
+ * A shorter version of struct dtv_property
+ * @cmd: Property type
+ * @data: Property value
+ */
+struct dtv_property_short {
+ __u32 cmd;
+ __u32 data;
+};
+
/* num of properties cannot exceed DTV_IOCTL_MAX_MSGS per ioctl */
#define DTV_IOCTL_MAX_MSGS 64

@@ -484,6 +495,18 @@ struct dtv_properties {
struct dtv_property *props;
};

+/**
+ * @struct dtv_properties_short
+ * A variant of struct dtv_properties
+ * to support struct dtv_property_short
+ * @num: Number of properties
+ * @props: Pointer to struct dtv_property_short
+ */
+struct dtv_properties_short {
+ __u32 num;
+ struct dtv_property_short *props;
+};
+
#if defined(__DVB_CORE__) || !defined (__KERNEL__)

/*
@@ -565,6 +588,7 @@ struct dvb_frontend_event {

#define FE_SET_PROPERTY _IOW('o', 82, struct dtv_properties)
#define FE_GET_PROPERTY _IOR('o', 83, struct dtv_properties)
+#define FE_SET_PROPERTY_SHORT _IOW('o', 84, struct dtv_properties_short)

/**
* When set, this flag will disable any zigzagging or other "normal" tuning
--
2.7.4
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