uevent mechanism
There are two ways for uevent to report events to user space:
1. Directly call executable programs or scripts in user space through the kmod module
2. Pass events from kernel space to user space through the netlink communication mechanism
About hotplug interface implementation and calling in modesetting_drv
void
drmmode_uevent_init(ScrnInfoPtr scrn, drmmode_ptr drmmode)
{
#ifdef CONFIG_UDEV_KMS
struct udev *u;
struct udev_monitor *mon;
u = udev_new();
if (!u)
return;
mon = udev_monitor_new_from_netlink(u, "udev");
if (!mon) {
udev_unref(u);
return;
}
if (udev_monitor_filter_add_match_subsystem_devtype(mon,
"drm",
"drm_minor") < 0 ||
udev_monitor_enable_receiving(mon) < 0) {
udev_monitor_unref(mon);
udev_unref(u);
return;
}
drmmode->uevent_handler =
xf86AddGeneralHandler(udev_monitor_get_fd(mon),
drmmode_handle_uevents, drmmode);
drmmode->uevent_monitor = mon;
#endif
}
The following is the processing function:
#ifdef CONFIG_UDEV_KMS
static void
drmmode_handle_uevents(int fd, void *closure)
{
drmmode_ptr drmmode = closure;
struct udev_device *dev;
Bool found = FALSE;
while ((dev = udev_monitor_receive_device(drmmode->uevent_monitor))) {
udev_device_unref(dev);
found = TRUE;
}
if (!found)
return;
drmmode_update_kms_state(drmmode);
}
#endif
The main processing content is drmmode_update_kms_state(), as shown in the following code:
#define DRM_MODE_LINK_STATUS_GOOD 0
#define DRM_MODE_LINK_STATUS_BAD 1
void
drmmode_update_kms_state(drmmode_ptr drmmode)
{
ScrnInfoPtr scrn = drmmode->scrn;
drmModeResPtr mode_res;
xf86CrtcConfigPtr config = XF86_CRTC_CONFIG_PTR(scrn);
int i, j;
Bool found = FALSE;
Bool changed = FALSE;
/* Try to re-set the mode on all the connectors with a BAD link-state:
* This may happen if a link degrades and a new modeset is necessary, using
* different link-training parameters. If the kernel found that the current
* mode is not achievable anymore, it should have pruned the mode before
* sending the hotplug event. Try to re-set the currently-set mode to keep
* the display alive, this will fail if the mode has been pruned.
* In any case, we will send randr events for the Desktop Environment to
* deal with it, if it wants to.
*/
for (i = 0; i < config->num_output; i + + ) {
xf86OutputPtr output = config->output[i];
drmmode_output_private_ptr drmmode_output = output->driver_private;
drmmode_output_detect(output);
/* Get an updated view of the properties for the current connector and
* look for the link-status property
*/
for (j = 0; j < drmmode_output->num_props; j + + ) {
drmmode_prop_ptr p = & amp;drmmode_output->props[j];
if (!strcmp(p->mode_prop->name, "link-status")) {
if (p->value == DRM_MODE_LINK_STATUS_BAD) {
xf86CrtcPtr crtc = output->crtc;
if (!crtc)
continue;
/* the connector got a link failure, re-set the current mode */
drmmode_set_mode_major(crtc, & amp;crtc->mode, crtc->rotation,
crtc->x, crtc->y);
xf86DrvMsg(scrn->scrnIndex, X_WARNING,
"hotplug event: connector %u's link-state is BAD, "
"tried resetting the current mode. You may be left"
"with a black screen if this fails...\\
",
drmmode_output->mode_output->connector_id);
}
break;
}
}
}
mode_res = drmModeGetResources(drmmode->fd);
if (!mode_res)
goto out;
if (mode_res->count_crtcs != config->num_crtc) {
/* this triggers with Zaphod mode where we don't currently support connector hotplug or MST. */
goto out_free_res;
}
/* figure out if we have gotten rid of any connectors
traverse old output list looking for outputs */
for (i = 0; i < config->num_output; i + + ) {
xf86OutputPtr output = config->output[i];
drmmode_output_private_ptr drmmode_output;
drmmode_output = output->driver_private;
found = FALSE;
for (j = 0; j < mode_res->count_connectors; j + + ) {
if (mode_res->connectors[j] == drmmode_output->output_id) {
found = TRUE;
break;
}
}
if(found)
continue;
drmModeFreeConnector(drmmode_output->mode_output);
drmmode_output->mode_output = NULL;
drmmode_output->output_id = -1;
changed = TRUE;
}
/* find new output ids we don't have outputs for */
for (i = 0; i < mode_res->count_connectors; i + + ) {
found = FALSE;
for (j = 0; j < config->num_output; j + + ) {
xf86OutputPtr output = config->output[j];
drmmode_output_private_ptr drmmode_output;
drmmode_output = output->driver_private;
if (mode_res->connectors[i] == drmmode_output->output_id) {
found = TRUE;
break;
}
}
if(found)
continue;
changed = TRUE;
drmmode_output_init(scrn, drmmode, mode_res, i, TRUE, 0);
}
if (changed) {
RRSetChanged(xf86ScrnToScreen(scrn));
RRTellChanged(xf86ScrnToScreen(scrn));
}
out_free_res:
/* Check to see if a lessee has disappeared */
drmmode_validate_leases(scrn);
drmModeFreeResources(mode_res);
out:
RRGetInfo(xf86ScrnToScreen(scrn), TRUE);
}
#undef DRM_MODE_LINK_STATUS_BAD
#undef DRM_MODE_LINK_STATUS_GOOD
Pay attention to drmmode_output_detect() below:
static xf86OutputStatus
drmmode_output_detect(xf86OutputPtr output)
{
/* go to the hw and retrieve a new output struct */
drmmode_output_private_ptr drmmode_output = output->driver_private;
drmmode_ptr drmmode = drmmode_output->drmmode;
xf86OutputStatus status;
if (drmmode_output->output_id == -1)
return XF86OutputStatusDisconnected;
drmModeFreeConnector(drmmode_output->mode_output);
drmmode_output->mode_output =
drmModeGetConnector(drmmode->fd, drmmode_output->output_id);
if (!drmmode_output->mode_output) {
drmmode_output->output_id = -1;
return XF86OutputStatusDisconnected;
}
drmmode_output_update_properties(output);
switch (drmmode_output->mode_output->connection) {
case DRM_MODE_CONNECTED:
status = XF86OutputStatusConnected;
break;
case DRM_MODE_DISCONNECTED:
status = XF86OutputStatusDisconnected;
break;
default:
case DRM_MODE_UNKNOWNCONNECTION:
status = XF86OutputStatusUnknown;
break;
}
return status;
}
The output_id is the connector_id; drmModeFreeConnector releases the drmModeConnectorPtr structure allocated by drmModeGetConnector; the function of drmModeGetConnector is to obtain a drmModeConnectorPtr structure if the connector_id is valid. The following mainly looks at drmmode_output_update_properties():
/*
* Update all of the property values for an output
*/
static void
drmmode_output_update_properties(xf86OutputPtr output)
{
drmmode_output_private_ptr drmmode_output = output->driver_private;
int i, j, k;
int err;
drmModeConnectorPtr koutput;
/* Use the most recently fetched values from the kernel */
koutput = drmmode_output->mode_output;
if (!koutput)
return;
for (i = 0; i < drmmode_output->num_props; i + + ) {
drmmode_prop_ptr p = & amp;drmmode_output->props[i];
for (j = 0; koutput & amp; & amp; j < koutput->count_props; j + + ) {
if (koutput->props[j] == p->mode_prop->prop_id) {
/* Check to see if the property value has changed */
if (koutput->prop_values[j] != p->value) {
p->value = koutput->prop_values[j];
if (p->mode_prop->flags & amp; DRM_MODE_PROP_RANGE) {
INT32 value = p->value;
err = RRChangeOutputProperty(output->randr_output, p->atoms[0],
XA_INTEGER, 32, PropModeReplace, 1,
& amp;value, FALSE, TRUE);
if (err != 0) {
xf86DrvMsg(output->scrn->scrnIndex, X_ERROR,
"RRChangeOutputProperty error, %d\\
", err);
}
}
else if (p->mode_prop->flags & amp; DRM_MODE_PROP_ENUM) {
for (k = 0; k < p->mode_prop->count_enums; k + + )
if (p->mode_prop->enums[k].value == p->value)
break;
if (k < p->mode_prop->count_enums) {
err = RRChangeOutputProperty(output->randr_output, p->atoms[0],
XA_ATOM, 32, PropModeReplace, 1,
& amp;p->atoms[k + 1], FALSE, TRUE);
if (err != 0) {
xf86DrvMsg(output->scrn->scrnIndex, X_ERROR,
"RRChangeOutputProperty error, %d\\
", err);
}
}
}
}
break;
}
}
}
/* Update the CTM property */
if (drmmode_output->ctm_atom) {
err = RRChangeOutputProperty(output->randr_output,
drmmode_output->ctm_atom,
XA_INTEGER, 32, PropModeReplace, 18,
& amp;drmmode_output->ctm,
FALSE, TRUE);
if (err != 0) {
xf86DrvMsg(output->scrn->scrnIndex, X_ERROR,
"RRChangeOutputProperty error, %d\\
", err);
}
}
}
Update randr display parameters through RRChangeOutputProperty().
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