linux-kernel - [PATCH v2] powerpc: silence a -Wcast-function-type warning in dawr_write_file

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Message-Id: <20190515135146.5866-1-malat@debian.org>
Date:   Wed, 15 May 2019 15:51:46 +0200
From:   Mathieu Malaterre <malat@...ian.org>
To:     Michael Ellerman <mpe@...erman.id.au>
Cc:     Mathieu Malaterre <malat@...ian.org>,
        Christoph Hellwig <hch@...radead.org>,
        Michael Neuling <mikey@...ling.org>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: [PATCH v2] powerpc: silence a -Wcast-function-type warning in dawr_write_file_bool

In commit c1fe190c0672 ("powerpc: Add force enable of DAWR on P9
option") the following piece of code was added:

   smp_call_function((smp_call_func_t)set_dawr, &null_brk, 0);

Since GCC 8 this triggers the following warning about incompatible
function types:

  arch/powerpc/kernel/hw_breakpoint.c:408:21: error: cast between incompatible function types from 'int (*)(struct arch_hw_breakpoint *)' to 'void (*)(void *)' [-Werror=cast-function-type]

Since the warning is there for a reason, and should not be hidden behind
a cast, provide an intermediate callback function to avoid the warning.

Fixes: c1fe190c0672 ("powerpc: Add force enable of DAWR on P9 option")
Suggested-by: Christoph Hellwig <hch@...radead.org>
Cc: Michael Neuling <mikey@...ling.org>
Signed-off-by: Mathieu Malaterre <malat@...ian.org>
---
v2: do not hide warning using a hack

 arch/powerpc/kernel/hw_breakpoint.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/kernel/hw_breakpoint.c b/arch/powerpc/kernel/hw_breakpoint.c
index f70fb89dbf60..969092d84a2f 100644
--- a/arch/powerpc/kernel/hw_breakpoint.c
+++ b/arch/powerpc/kernel/hw_breakpoint.c
@@ -386,6 +386,11 @@ void hw_breakpoint_pmu_read(struct perf_event *bp)
 bool dawr_force_enable;
 EXPORT_SYMBOL_GPL(dawr_force_enable);
 
+static void set_dawr_cb(void *info)
+{
+	set_dawr(info);
+}
+
 static ssize_t dawr_write_file_bool(struct file *file,
 				    const char __user *user_buf,
 				    size_t count, loff_t *ppos)
@@ -405,7 +410,7 @@ static ssize_t dawr_write_file_bool(struct file *file,
 
 	/* If we are clearing, make sure all CPUs have the DAWR cleared */
 	if (!dawr_force_enable)
-		smp_call_function((smp_call_func_t)set_dawr, &null_brk, 0);
+		smp_call_function(set_dawr_cb, &null_brk, 0);
 
 	return rc;
 }
-- 
2.20.1