resume: Write resume_offset attribute

Support for a device offset as part of the string written to
/sys/power/resume never got into a mainline kernel.

However, since Linux 4.17 there is a separate resume_offset attribute
that we can use to set the offset before attempting to resume.

Change resume() to write the resume_offset attribute instead.

Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Gbp-Pq: Name resume-write-resume_offset-parameter.patch

diff --git a/usr/kinit/resume/resumelib.c b/usr/kinit/resume/resumelib.c
index e557b05c050b2abe2b312c27604d6141134c1545..03e596a47d04e6daf8fbb3849fa7dd3464a8ea8c 100644 (file)
--- a/usr/kinit/resume/resumelib.c
+++ b/usr/kinit/resume/resumelib.c
@@ -44,8 +44,8 @@ int do_resume(int argc, char *argv[])
 int resume(const char *resume_file, unsigned long long resume_offset)
 {
        dev_t resume_device;
-       int powerfd = -1;
-       char device_string[64];
+       int attr_fd = -1;
+       char attr_value[64];
        int len;
 
        resume_device = name_to_dev_t(resume_file);
@@ -55,30 +55,50 @@ int resume(const char *resume_file, unsigned long long resume_offset)
                goto failure;
        }
 
-       if ((powerfd = open("/sys/power/resume", O_WRONLY)) < 0)
-               goto fail_r;
+       if ((attr_fd = open("/sys/power/resume_offset", O_WRONLY)) < 0)
+               goto fail_offset;
 
-       len = snprintf(device_string, sizeof device_string,
-                      "%u:%u:%llu",
-                      major(resume_device), minor(resume_device),
+       len = snprintf(attr_value, sizeof attr_value,
+                      "%llu",
                       resume_offset);
 
        /* This should never happen */
-       if (len >= sizeof device_string)
+       if (len >= sizeof attr_value)
+               goto fail_offset;
+
+       if (write(attr_fd, attr_value, len) != len)
+               goto fail_offset;
+
+       close(attr_fd);
+
+       if ((attr_fd = open("/sys/power/resume", O_WRONLY)) < 0)
+               goto fail_r;
+
+       len = snprintf(attr_value, sizeof attr_value,
+                      "%u:%u",
+                      major(resume_device), minor(resume_device));
+
+       /* This should never happen */
+       if (len >= sizeof attr_value)
                goto fail_r;
 
        dprintf("kinit: trying to resume from %s\n", resume_file);
 
-       if (write(powerfd, device_string, len) != len)
+       if (write(attr_fd, attr_value, len) != len)
                goto fail_r;
 
        /* Okay, what are we still doing alive... */
 failure:
-       if (powerfd >= 0)
-               close(powerfd);
+       if (attr_fd >= 0)
+               close(attr_fd);
        dprintf("kinit: No resume image, doing normal boot...\n");
        return -1;
 
+fail_offset:
+       fprintf(stderr, "Cannot write /sys/power/resume_offset "
+                       "(no software suspend kernel support, or old kernel version?)\n");
+       goto failure;
+
 fail_r:
        fprintf(stderr, "Cannot write /sys/power/resume "
                        "(no software suspend kernel support?)\n");