Revision 6af8ae321a801a4e20183454c65eb0d23069d8ac authored by Phil Elwell on 28 January 2021, 11:30:04 UTC, committed by Phil Elwell on 28 January 2021, 11:46:41 UTC
A relatively recent commit ([1]) contained optimisation for the PIO SPI FIFO-filling functions. The commit message includes the phrase "[t]he blind and counted loops are always called with nonzero count". This is technically true, but it is still possible for count to become zero before the loop is entered - if tfr->len is zero. Moving the loop exit condition to the end of the loop saves a few cycles, but results in a near-infinite loop should the revised count be zero on entry. Strangely, zero-lengthed transfers aren't filtered by the SPI framework and, even more strangely, the Python3 spidev library is triggering them for no obvious reason. Avoid the problem completely by bailing out of the main transfer function early if trf->len is zero, although there may be a case for moving the mitigation into the framework. See: https://github.com/raspberrypi/linux/issues/4100 Signed-off-by: Phil Elwell <phil@raspberrypi.com> [1] 26751de25d25 ("spi: bcm2835: Micro-optimise FIFO loops")
1 parent c5f51df
diffconfig
#!/usr/bin/python
# SPDX-License-Identifier: GPL-2.0
#
# diffconfig - a tool to compare .config files.
#
# originally written in 2006 by Matt Mackall
# (at least, this was in his bloatwatch source code)
# last worked on 2008 by Tim Bird
#
import sys, os
def usage():
print("""Usage: diffconfig [-h] [-m] [<config1> <config2>]
Diffconfig is a simple utility for comparing two .config files.
Using standard diff to compare .config files often includes extraneous and
distracting information. This utility produces sorted output with only the
changes in configuration values between the two files.
Added and removed items are shown with a leading plus or minus, respectively.
Changed items show the old and new values on a single line.
If -m is specified, then output will be in "merge" style, which has the
changed and new values in kernel config option format.
If no config files are specified, .config and .config.old are used.
Example usage:
$ diffconfig .config config-with-some-changes
-EXT2_FS_XATTR n
CRAMFS n -> y
EXT2_FS y -> n
LOG_BUF_SHIFT 14 -> 16
PRINTK_TIME n -> y
""")
sys.exit(0)
# returns a dictionary of name/value pairs for config items in the file
def readconfig(config_file):
d = {}
for line in config_file:
line = line[:-1]
if line[:7] == "CONFIG_":
name, val = line[7:].split("=", 1)
d[name] = val
if line[-11:] == " is not set":
d[line[9:-11]] = "n"
return d
def print_config(op, config, value, new_value):
global merge_style
if merge_style:
if new_value:
if new_value=="n":
print("# CONFIG_%s is not set" % config)
else:
print("CONFIG_%s=%s" % (config, new_value))
else:
if op=="-":
print("-%s %s" % (config, value))
elif op=="+":
print("+%s %s" % (config, new_value))
else:
print(" %s %s -> %s" % (config, value, new_value))
def main():
global merge_style
# parse command line args
if ("-h" in sys.argv or "--help" in sys.argv):
usage()
merge_style = 0
if "-m" in sys.argv:
merge_style = 1
sys.argv.remove("-m")
argc = len(sys.argv)
if not (argc==1 or argc == 3):
print("Error: incorrect number of arguments or unrecognized option")
usage()
if argc == 1:
# if no filenames given, assume .config and .config.old
build_dir=""
if "KBUILD_OUTPUT" in os.environ:
build_dir = os.environ["KBUILD_OUTPUT"]+"/"
configa_filename = build_dir + ".config.old"
configb_filename = build_dir + ".config"
else:
configa_filename = sys.argv[1]
configb_filename = sys.argv[2]
try:
a = readconfig(open(configa_filename))
b = readconfig(open(configb_filename))
except (IOError):
e = sys.exc_info()[1]
print("I/O error[%s]: %s\n" % (e.args[0],e.args[1]))
usage()
# print items in a but not b (accumulate, sort and print)
old = []
for config in a:
if config not in b:
old.append(config)
old.sort()
for config in old:
print_config("-", config, a[config], None)
del a[config]
# print items that changed (accumulate, sort, and print)
changed = []
for config in a:
if a[config] != b[config]:
changed.append(config)
else:
del b[config]
changed.sort()
for config in changed:
print_config("->", config, a[config], b[config])
del b[config]
# now print items in b but not in a
# (items from b that were in a were removed above)
new = sorted(b.keys())
for config in new:
print_config("+", config, None, b[config])
main()
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