package/base-files: caldata: work around dd's limitation

[openwrt/openwrt.git] / package / base-files / files / lib / functions / caldata.sh

diff --git a/package/base-files/files/lib/functions/caldata.sh b/package/base-files/files/lib/functions/caldata.sh
index 6862da716436c64f9ff6177dbcb01a8f9959edd7..e22c7d27e69f469bc87021b515d3a20ae749be67 100644 (file)
--- a/package/base-files/files/lib/functions/caldata.sh
+++ b/package/base-files/files/lib/functions/caldata.sh
@@ -64,7 +64,8 @@ caldata_from_file() {
 
        [ -n "$target" ] || target=/lib/firmware/$FIRMWARE
 
-       dd if=$source of=$target iflag=skip_bytes bs=$count skip=$offset count=1 2>/dev/null || \
+       # dd doesn't handle partial reads from special files: use cat
+       cat $source | dd of=$target iflag=skip_bytes bs=$count skip=$offset count=1 2>/dev/null || \
                caldata_die "failed to extract calibration data from $source"
 }
 
@@ -73,13 +74,14 @@ caldata_sysfsload_from_file() {
        local offset=$(($2))
        local count=$(($3))
 
+       # dd doesn't handle partial reads from special files: use cat
        # test extract to /dev/null first
-       dd if=$source of=/dev/null iflag=skip_bytes bs=$count skip=$offset count=1 2>/dev/null || \
+       cat $source | dd of=/dev/null iflag=skip_bytes bs=$count skip=$offset count=1 2>/dev/null || \
                caldata_die "failed to extract calibration data from $source"
 
        # can't fail now
        echo 1 > /sys/$DEVPATH/loading
-       dd if=$source of=/sys/$DEVPATH/data iflag=skip_bytes bs=$count skip=$offset count=1 2>/dev/null
+       cat $source | dd of=/sys/$DEVPATH/data iflag=skip_bytes bs=$count skip=$offset count=1 2>/dev/null
        echo 0 > /sys/$DEVPATH/loading
 }