From 0fb2ef3aaecbde97459ec6d94d73d22718e62aae Mon Sep 17 00:00:00 2001
From: Richard Hughes <richard@hughsie.com>
Date: Thu, 4 Nov 2021 14:45:31 +0000
Subject: [PATCH] trivial: Add fu_udev_device_seek() for future code

---
 libfwupdplugin/fu-udev-device.c | 51 +++++++++++++++++++++++++++++++++
 libfwupdplugin/fu-udev-device.h |  2 ++
 libfwupdplugin/fwupdplugin.map  |  1 +
 3 files changed, 54 insertions(+)

diff --git a/libfwupdplugin/fu-udev-device.c b/libfwupdplugin/fu-udev-device.c
index 16b591c38..a0c891e8e 100644
--- a/libfwupdplugin/fu-udev-device.c
+++ b/libfwupdplugin/fu-udev-device.c
@@ -1447,6 +1447,57 @@ fu_udev_device_pread_full(FuUdevDevice *self,
 #endif
 }
 
+/**
+ * fu_udev_device_seek:
+ * @self: a #FuUdevDevice
+ * @offset: offset address
+ * @error: (nullable): optional return location for an error
+ *
+ * Seeks a file descriptor to a given offset.
+ *
+ * Returns: %TRUE for success
+ *
+ * Since: 1.7.2
+ **/
+gboolean
+fu_udev_device_seek(FuUdevDevice *self, goffset offset, GError **error)
+{
+	FuUdevDevicePrivate *priv = GET_PRIVATE(self);
+
+	g_return_val_if_fail(FU_IS_UDEV_DEVICE(self), FALSE);
+	g_return_val_if_fail(error == NULL || *error == NULL, FALSE);
+
+	/* not open! */
+	if (priv->fd == 0) {
+		g_set_error(error,
+			    FWUPD_ERROR,
+			    FWUPD_ERROR_INTERNAL,
+			    "%s [%s] has not been opened",
+			    fu_device_get_id(FU_DEVICE(self)),
+			    fu_device_get_name(FU_DEVICE(self)));
+		return FALSE;
+	}
+
+#ifdef HAVE_PWRITE
+	if (lseek(priv->fd, offset, SEEK_SET) < 0) {
+		g_set_error(error,
+			    G_IO_ERROR,
+			    G_IO_ERROR_FAILED,
+			    "failed to seek to 0x%04x: %s",
+			    (guint)offset,
+			    strerror(errno));
+		return FALSE;
+	}
+	return TRUE;
+#else
+	g_set_error_literal(error,
+			    FWUPD_ERROR,
+			    FWUPD_ERROR_NOT_SUPPORTED,
+			    "Not supported as lseek() is unavailable");
+	return FALSE;
+#endif
+}
+
 /**
  * fu_udev_device_pwrite_full:
  * @self: a #FuUdevDevice
diff --git a/libfwupdplugin/fu-udev-device.h b/libfwupdplugin/fu-udev-device.h
index 106a97cb5..d930674b9 100644
--- a/libfwupdplugin/fu-udev-device.h
+++ b/libfwupdplugin/fu-udev-device.h
@@ -113,6 +113,8 @@ fu_udev_device_pread_full(FuUdevDevice *self,
 			  guint8 *buf,
 			  gsize bufsz,
 			  GError **error) G_GNUC_WARN_UNUSED_RESULT;
+gboolean
+fu_udev_device_seek(FuUdevDevice *self, goffset offset, GError **error) G_GNUC_WARN_UNUSED_RESULT;
 const gchar *
 fu_udev_device_get_sysfs_attr(FuUdevDevice *self, const gchar *attr, GError **error);
 gboolean
diff --git a/libfwupdplugin/fwupdplugin.map b/libfwupdplugin/fwupdplugin.map
index 543a81736..8ee52fd80 100644
--- a/libfwupdplugin/fwupdplugin.map
+++ b/libfwupdplugin/fwupdplugin.map
@@ -950,5 +950,6 @@ LIBFWUPDPLUGIN_1.7.2 {
   global:
     fu_context_has_hwid_flag;
     fu_udev_device_get_sysfs_attr_uint64;
+    fu_udev_device_seek;
   local: *;
 } LIBFWUPDPLUGIN_1.7.1;