From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D23188BE7 for ; Tue, 8 Nov 2022 15:34:18 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 02A06C433D7; Tue, 8 Nov 2022 15:34:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1667921658; bh=QULdRw93pmvMhegOa4ePuSQURnFlXlrdf9tEjj03QEU=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=vLDabxVgpbNTSTwEWB3ZHvOVjlO8SaGNBAcpiztSlSLwy7uH3nCw2udS/4Wus2EI3 553gkZ9ijOdEjlDteLyE+agQjchnFbdCpsTrsV6IOTd84rRivdmZHcKiYSd76/6Mse 33yNLzFtCtTN/aOWcjNQQAyfEqc/qi2w0iDOw5wU= Date: Tue, 8 Nov 2022 16:34:15 +0100 From: Greg Kroah-Hartman To: Deepak R Varma Cc: linux-staging@lists.linux.dev, linux-kernel@vger.kernel.org Subject: Re: staging/wlan-ng query: convert to flexible array member Message-ID: References: Precedence: bulk X-Mailing-List: linux-staging@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Tue, Nov 08, 2022 at 08:42:59PM +0530, Deepak R Varma wrote: > Hello, > > First, my apologies for the long email. > I am requesting guidance on how to approach resolving the zero element flexible > VLO struct implementation in this driver in file drivers/staging/waln-ng/hfa384x.f > > The struct hfa384x_pdrec contains nested structs with zero element arrays. These > zero element structs are part of a union 'data' inside the struct container. This > union 'data' is the last element of this container. Please see the code snip below: > > > > 1068 struct hfa384x_pdrec { > 1 __le16 len; /* in words */ > 2 __le16 code; > 3 union pdr { > 4 struct hfa384x_pdr_pcb_partnum pcb_partnum; > 11 struct hfa384x_pdr_nicid nicid; > 12 struct hfa384x_pdr_refdac_measurements refdac_measurements; > 13 struct hfa384x_pdr_vgdac_measurements vgdac_measurements; > 14 struct hfa384x_pdr_level_comp_measurements level_compc_measurements; > 15 struct hfa384x_pdr_mac_address mac_address; > 39 } data; > 40 } __packed; > > > > The three structures in question are declared as follows in the same file: > > > 962 struct hfa384x_pdr_refdac_measurements { > 1 u16 value[0]; > 2 } __packed; > 3 > 4 struct hfa384x_pdr_vgdac_measurements { > 5 u16 value[0]; > 6 } __packed; > 7 > 8 struct hfa384x_pdr_level_comp_measurements { > 9 u16 value[0]; > 10 } __packed; > > > As per the C99 specifications, the flexible array struct should have at least > one member other than the true flexible array member. So converting these from > [0] to [] is not feasible in the current form. > > I did not find these struct variables being used for memory allocation in the > code directly. My find may be short since the implementation appears to get very > complex as I tried to get deeper. > > Can you please suggest how should I approach correcting the zero element flex > array implementation here? Can these structs be removed if they are unused? Are you sure they are unused? They look like structures that are read from the memory of a device, right? Try removing the structures from the union and see what happens :) thanks, greg k-h