Adding upstream version 255.4.upstream/255.4

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 250 insertions, 0 deletions

diff --git a/src/login/logind-brightness.c b/src/login/logind-brightness.c
new file mode 100644
index 0000000..40bcb39
--- /dev/null
+++ b/src/login/logind-brightness.c
@@ -0,0 +1,250 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include "bus-util.h"
+#include "device-util.h"
+#include "hash-funcs.h"
+#include "logind-brightness.h"
+#include "logind.h"
+#include "process-util.h"
+#include "stdio-util.h"
+
+/* Brightness and LED devices tend to be very slow to write to (often being I2C and such). Writes to the
+ * sysfs attributes are synchronous, and hence will freeze our process on access. We can't really have that,
+ * hence we add some complexity: whenever we need to write to the brightness attribute, we do so in a forked
+ * off process, which terminates when it is done. Watching that process allows us to watch completion of the
+ * write operation.
+ *
+ * To make this even more complex: clients are likely to send us many write requests in a short time-frame
+ * (because they implement reactive brightness sliders on screen). Let's coalesce writes to make this
+ * efficient: whenever we get requests to change brightness while we are still writing to the brightness
+ * attribute, let's remember the request and restart a new one when the initial operation finished. When we
+ * get another request while one is ongoing and one is pending we'll replace the pending one with the new
+ * one.
+ *
+ * The bus messages are answered when the first write operation finishes that started either due to the
+ * request or due to a later request that overrode the requested one.
+ *
+ * Yes, this is complex, but I don't see an easier way if we want to be both efficient and still support
+ * completion notification. */
+
+typedef struct BrightnessWriter {
+        Manager *manager;
+
+        sd_device *device;
+        char *path;
+
+        pid_t child;
+
+        uint32_t brightness;
+        bool again;
+
+        Set *current_messages;
+        Set *pending_messages;
+
+        sd_event_source* child_event_source;
+} BrightnessWriter;
+
+static BrightnessWriter* brightness_writer_free(BrightnessWriter *w) {
+        if (!w)
+                return NULL;
+
+        if (w->manager && w->path)
+                (void) hashmap_remove_value(w->manager->brightness_writers, w->path, w);
+
+        sd_device_unref(w->device);
+        free(w->path);
+
+        set_free(w->current_messages);
+        set_free(w->pending_messages);
+
+        w->child_event_source = sd_event_source_unref(w->child_event_source);
+
+        return mfree(w);
+}
+
+DEFINE_TRIVIAL_CLEANUP_FUNC(BrightnessWriter*, brightness_writer_free);
+
+DEFINE_PRIVATE_HASH_OPS_WITH_VALUE_DESTRUCTOR(
+                brightness_writer_hash_ops,
+                char,
+                string_hash_func,
+                string_compare_func,
+                BrightnessWriter,
+                brightness_writer_free);
+
+static void brightness_writer_reply(BrightnessWriter *w, int error) {
+        int r;
+
+        assert(w);
+
+        for (;;) {
+                _cleanup_(sd_bus_message_unrefp) sd_bus_message *m = NULL;
+
+                m = set_steal_first(w->current_messages);
+                if (!m)
+                        break;
+
+                if (error == 0)
+                        r = sd_bus_reply_method_return(m, NULL);
+                else
+                        r = sd_bus_reply_method_errnof(m, error, "Failed to write to brightness device: %m");
+                if (r < 0)
+                        log_warning_errno(r, "Failed to send method reply, ignoring: %m");
+        }
+}
+
+static int brightness_writer_fork(BrightnessWriter *w);
+
+static int on_brightness_writer_exit(sd_event_source *s, const siginfo_t *si, void *userdata) {
+        BrightnessWriter *w = ASSERT_PTR(userdata);
+        int r;
+
+        assert(s);
+        assert(si);
+
+        assert(si->si_pid == w->child);
+        w->child = 0;
+        w->child_event_source = sd_event_source_unref(w->child_event_source);
+
+        brightness_writer_reply(w,
+                                si->si_code == CLD_EXITED &&
+                                si->si_status == EXIT_SUCCESS ? 0 : -EPROTO);
+
+        if (w->again) {
+                /* Another request to change the brightness has been queued. Act on it, but make the pending
+                 * messages the current ones. */
+                w->again = false;
+                set_free(w->current_messages);
+                w->current_messages = TAKE_PTR(w->pending_messages);
+
+                r = brightness_writer_fork(w);
+                if (r >= 0)
+                        return 0;
+
+                brightness_writer_reply(w, r);
+        }
+
+        brightness_writer_free(w);
+        return 0;
+}
+
+static int brightness_writer_fork(BrightnessWriter *w) {
+        int r;
+
+        assert(w);
+        assert(w->manager);
+        assert(w->child == 0);
+        assert(!w->child_event_source);
+
+        r = safe_fork("(sd-bright)", FORK_DEATHSIG_SIGKILL|FORK_REARRANGE_STDIO|FORK_CLOSE_ALL_FDS|FORK_LOG|FORK_REOPEN_LOG, &w->child);
+        if (r < 0)
+                return r;
+        if (r == 0) {
+                char brs[DECIMAL_STR_MAX(uint32_t)+1];
+
+                /* Child */
+                xsprintf(brs, "%" PRIu32, w->brightness);
+
+                r = sd_device_set_sysattr_value(w->device, "brightness", brs);
+                if (r < 0) {
+                        log_device_error_errno(w->device, r, "Failed to write brightness to device: %m");
+                        _exit(EXIT_FAILURE);
+                }
+
+                _exit(EXIT_SUCCESS);
+        }
+
+        r = sd_event_add_child(w->manager->event, &w->child_event_source, w->child, WEXITED, on_brightness_writer_exit, w);
+        if (r < 0)
+                return log_error_errno(r, "Failed to watch brightness writer child " PID_FMT ": %m", w->child);
+
+        return 0;
+}
+
+static int set_add_message(Set **set, sd_bus_message *message) {
+        int r;
+
+        assert(set);
+
+        if (!message)
+                return 0;
+
+        r = sd_bus_message_get_expect_reply(message);
+        if (r <= 0)
+                return r;
+
+        r = set_ensure_put(set, &bus_message_hash_ops, message);
+        if (r <= 0)
+                return r;
+        sd_bus_message_ref(message);
+
+        return 1;
+}
+
+int manager_write_brightness(
+                Manager *m,
+                sd_device *device,
+                uint32_t brightness,
+                sd_bus_message *message) {
+
+        _cleanup_(brightness_writer_freep) BrightnessWriter *w = NULL;
+        BrightnessWriter *existing;
+        const char *path;
+        int r;
+
+        assert(m);
+        assert(device);
+
+        r = sd_device_get_syspath(device, &path);
+        if (r < 0)
+                return log_device_error_errno(device, r, "Failed to get sysfs path for brightness device: %m");
+
+        existing = hashmap_get(m->brightness_writers, path);
+        if (existing) {
+                /* There's already a writer for this device. Let's update it with the new brightness, and add
+                 * our message to the set of message to reply when done. */
+
+                r = set_add_message(&existing->pending_messages, message);
+                if (r < 0)
+                        return log_error_errno(r, "Failed to add message to set: %m");
+
+                /* We override any previously requested brightness here: we coalesce writes, and the newest
+                 * requested brightness is the one we'll put into effect. */
+                existing->brightness = brightness;
+                existing->again = true; /* request another iteration of the writer when the current one is
+                                         * complete */
+                return 0;
+        }
+
+        w = new(BrightnessWriter, 1);
+        if (!w)
+                return log_oom();
+
+        *w = (BrightnessWriter) {
+                .device = sd_device_ref(device),
+                .path = strdup(path),
+                .brightness = brightness,
+        };
+
+        if (!w->path)
+                return log_oom();
+
+        r = hashmap_ensure_put(&m->brightness_writers, &brightness_writer_hash_ops, w->path, w);
+        if (r == -ENOMEM)
+                return log_oom();
+        if (r < 0)
+                return log_error_errno(r, "Failed to add brightness writer to hashmap: %m");
+
+        w->manager = m;
+
+        r = set_add_message(&w->current_messages, message);
+        if (r < 0)
+                return log_error_errno(r, "Failed to add message to set: %m");
+
+        r = brightness_writer_fork(w);
+        if (r < 0)
+                return r;
+
+        TAKE_PTR(w);
+        return 0;
+}