linux-kernel - [PATCH 11/17] tty: hvc_console: use flexible array for outbuf

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Message-ID: <20231121092258.9334-12-jirislaby@kernel.org>
Date:   Tue, 21 Nov 2023 10:22:52 +0100
From:   "Jiri Slaby (SUSE)" <jirislaby@...nel.org>
To:     gregkh@...uxfoundation.org
Cc:     linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org,
        "Jiri Slaby (SUSE)" <jirislaby@...nel.org>,
        linuxppc-dev@...ts.ozlabs.org
Subject: [PATCH 11/17] tty: hvc_console: use flexible array for outbuf

This means:
* move outbuf to the end of struct hvc_struct and convert from pointer
  to flexible array (the structure is smaller now)
* use struct_size() at the allocation site
* align outbuf in the struct instead of ALIGN() at kzalloc()

And apart from the above, use u8 instead of char (which are the same
thanks to -funsigned-char). The former is now preferred over the latter.

It makes the code easier to understand.

Signed-off-by: Jiri Slaby (SUSE) <jirislaby@...nel.org>
Cc: linuxppc-dev@...ts.ozlabs.org
---
 drivers/tty/hvc/hvc_console.c | 4 +---
 drivers/tty/hvc/hvc_console.h | 2 +-
 2 files changed, 2 insertions(+), 4 deletions(-)

diff --git a/drivers/tty/hvc/hvc_console.c b/drivers/tty/hvc/hvc_console.c
index 959fae54ca39..93b613e1f176 100644
--- a/drivers/tty/hvc/hvc_console.c
+++ b/drivers/tty/hvc/hvc_console.c
@@ -922,8 +922,7 @@ struct hvc_struct *hvc_alloc(uint32_t vtermno, int data,
 			return ERR_PTR(err);
 	}
 
-	hp = kzalloc(ALIGN(sizeof(*hp), sizeof(long)) + outbuf_size,
-			GFP_KERNEL);
+	hp = kzalloc(struct_size(hp, outbuf, outbuf_size), GFP_KERNEL);
 	if (!hp)
 		return ERR_PTR(-ENOMEM);
 
@@ -931,7 +930,6 @@ struct hvc_struct *hvc_alloc(uint32_t vtermno, int data,
 	hp->data = data;
 	hp->ops = ops;
 	hp->outbuf_size = outbuf_size;
-	hp->outbuf = &((char *)hp)[ALIGN(sizeof(*hp), sizeof(long))];
 
 	tty_port_init(&hp->port);
 	hp->port.ops = &hvc_port_ops;
diff --git a/drivers/tty/hvc/hvc_console.h b/drivers/tty/hvc/hvc_console.h
index 9668f821db01..b718714bf399 100644
--- a/drivers/tty/hvc/hvc_console.h
+++ b/drivers/tty/hvc/hvc_console.h
@@ -37,7 +37,6 @@ struct hvc_struct {
 	spinlock_t lock;
 	int index;
 	int do_wakeup;
-	char *outbuf;
 	int outbuf_size;
 	int n_outbuf;
 	uint32_t vtermno;
@@ -48,6 +47,7 @@ struct hvc_struct {
 	struct work_struct tty_resize;
 	struct list_head next;
 	unsigned long flags;
+	u8 outbuf[] __aligned(sizeof(long));
 };
 
 /* implemented by a low level driver */
-- 
2.42.1