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authorUlises Mendez Martinez <umendez@google.com>2026-09-04 15:07:09 +0000
committerJosh Poimboeuf <jpoimboe@kernel.org>2026-09-13 18:15:43 -0700
commit7e61560628d17ea6b1d8ee370f6d42694cff8758 (patch)
treee6080164b2f4c4c419894bdb3ce4d956ca9a98c5 /Documentation/driver-api/miscellaneous.rst
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objtool: Validate disassembler headers in libopcodes probegrafted
commit 3f2de814c059 ("objtool: Fix libopcodes linking with static libraries") tested for libopcodes availability by linking a test snippet with a forward declaration of disassemble_init_for_target(). However, testing symbol linkage with an extern declaration only verifies the presence of the library (.so/.a) and bypasses checking for development headers (binutils-dev). On systems where libopcodes is present without development headers installed, the probe succeeds, enabling BUILD_DISAS. Subsequent compilation of objtool then fails: fatal error: 'bfd.h' file not found 113 | #include <bfd.h> Additionally, the probe invokes $(HOSTCC) without $(HOSTCFLAGS), ignoring any sysroot or include flags specified for the host compiler. Fix this by including <bfd.h> and <dis-asm.h> directly in the test snippet, passing $(HOSTCFLAGS) so host compiler options are respected, and defining PACKAGE="objtool" to satisfy the configuration check in <bfd.h>. Fixes: 3f2de814c059 ("objtool: Fix libopcodes linking with static libraries") Fixes: 436326bc525d ("objtool: fix build failure due to missing libopcodes check") Reported-by: Alice Ryhl <aliceryhl@google.com> Assisted-by: Antigravity:Gemini-Next Signed-off-by: Ulises Mendez Martinez <umendez@google.com> Link: https://patch.msgid.link/20260904150710.2997558-1-umendez@google.com Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
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+Parallel Port Devices
+=====================
+
+.. kernel-doc:: include/linux/parport.h
+ :internal:
+
+.. kernel-doc:: drivers/parport/ieee1284.c
+ :export:
+
+.. kernel-doc:: drivers/parport/share.c
+ :export:
+
+.. kernel-doc:: drivers/parport/daisy.c
+ :internal:
+
+16x50 UART Driver
+=================
+
+.. kernel-doc:: drivers/tty/serial/8250/8250_core.c
+ :export:
+
+See serial/driver.rst for related APIs.
+
+Pulse-Width Modulation (PWM)
+============================
+
+Pulse-width modulation is a modulation technique primarily used to
+control power supplied to electrical devices.
+
+The PWM framework provides an abstraction for providers and consumers of
+PWM signals. A controller that provides one or more PWM signals is
+registered as :c:type:`struct pwm_chip <pwm_chip>`. Providers
+are expected to embed this structure in a driver-specific structure.
+This structure contains fields that describe a particular chip.
+
+A chip exposes one or more PWM signal sources, each of which exposed as
+a :c:type:`struct pwm_device <pwm_device>`. Operations can be
+performed on PWM devices to control the period, duty cycle, polarity and
+active state of the signal.
+
+Note that PWM devices are exclusive resources: they can always only be
+used by one consumer at a time.
+
+.. kernel-doc:: include/linux/pwm.h
+ :internal:
+
+.. kernel-doc:: drivers/pwm/core.c
+ :export: