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Subject: Re: [PATCH v9 5/6] Bluetooth: Refactor read default sys config for
 various types
From:   Marcel Holtmann <marcel@holtmann.org>
In-Reply-To: <20201111150115.v9.5.I9231b35b0be815c32c3a3ec48dcd1d68fa65daf4@changeid>
Date:   Wed, 11 Nov 2020 12:20:25 +0100
Cc:     linux-bluetooth <linux-bluetooth@vger.kernel.org>,
        Luiz Augusto von Dentz <luiz.dentz@gmail.com>,
        alainm@chromium.org, mmandlik@chromium.org, mcchou@chromium.org,
        "David S. Miller" <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>,
        Johan Hedberg <johan.hedberg@gmail.com>,
        linux-kernel@vger.kernel.org, netdev@vger.kernel.org
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Message-Id: <A5A4227D-58B7-4C08-AFC9-BC8A8D469179@holtmann.org>
References: <20201111150115.v9.1.I55fa38874edc240d726c1de6e82b2ce57b64f5eb@changeid>
 <20201111150115.v9.5.I9231b35b0be815c32c3a3ec48dcd1d68fa65daf4@changeid>
To:     Howard Chung <howardchung@google.com>
Precedence: bulk

Hi Howard,

> Refactor read default system configuration function so that it's capable
> of returning different types than u16
> 
> Signed-off-by: Howard Chung <howardchung@google.com>
> ---
> 
> (no changes since v8)
> 
> Changes in v8:
> - Update the commit title and message
> 
> net/bluetooth/mgmt_config.c | 140 +++++++++++++++++++++---------------
> 1 file changed, 84 insertions(+), 56 deletions(-)
> 
> diff --git a/net/bluetooth/mgmt_config.c b/net/bluetooth/mgmt_config.c
> index 2d3ad288c78ac..282fbf82f3192 100644
> --- a/net/bluetooth/mgmt_config.c
> +++ b/net/bluetooth/mgmt_config.c
> @@ -11,72 +11,100 @@
> #include "mgmt_util.h"
> #include "mgmt_config.h"
> 
> -#define HDEV_PARAM_U16(_param_code_, _param_name_) \
> -{ \
> -	{ cpu_to_le16(_param_code_), sizeof(__u16) }, \
> -	{ cpu_to_le16(hdev->_param_name_) } \
> -}
> +#define HDEV_PARAM_U16(_param_name_) \
> +	struct {\
> +		struct mgmt_tlv entry; \
> +		__le16 value; \
> +	} __packed _param_name_
> 
> -#define HDEV_PARAM_U16_JIFFIES_TO_MSECS(_param_code_, _param_name_) \
> -{ \
> -	{ cpu_to_le16(_param_code_), sizeof(__u16) }, \
> -	{ cpu_to_le16(jiffies_to_msecs(hdev->_param_name_)) } \
> -}
> +#define TLV_SET_U16(_param_code_, _param_name_) \
> +	{ \
> +		{ cpu_to_le16(_param_code_), sizeof(__u16) }, \
> +		cpu_to_le16(hdev->_param_name_) \
> +	}
> +
> +#define TLV_SET_U16_JIFFIES_TO_MSECS(_param_code_, _param_name_) \
> +	{ \
> +		{ cpu_to_le16(_param_code_), sizeof(__u16) }, \
> +		cpu_to_le16(jiffies_to_msecs(hdev->_param_name_)) \
> +	}
> 
> int read_def_system_config(struct sock *sk, struct hci_dev *hdev, void *data,
> 			   u16 data_len)
> {
> -	struct {
> -		struct mgmt_tlv entry;
> -		union {
> -			/* This is a simplification for now since all values
> -			 * are 16 bits.  In the future, this code may need
> -			 * refactoring to account for variable length values
> -			 * and properly calculate the required buffer size.
> -			 */
> -			__le16 value;
> -		};
> -	} __packed params[] = {
> +	int ret;
> +	struct mgmt_rp_read_def_system_config {
> 		/* Please see mgmt-api.txt for documentation of these values */
> -		HDEV_PARAM_U16(0x0000, def_page_scan_type),
> -		HDEV_PARAM_U16(0x0001, def_page_scan_int),
> -		HDEV_PARAM_U16(0x0002, def_page_scan_window),
> -		HDEV_PARAM_U16(0x0003, def_inq_scan_type),
> -		HDEV_PARAM_U16(0x0004, def_inq_scan_int),
> -		HDEV_PARAM_U16(0x0005, def_inq_scan_window),
> -		HDEV_PARAM_U16(0x0006, def_br_lsto),
> -		HDEV_PARAM_U16(0x0007, def_page_timeout),
> -		HDEV_PARAM_U16(0x0008, sniff_min_interval),
> -		HDEV_PARAM_U16(0x0009, sniff_max_interval),
> -		HDEV_PARAM_U16(0x000a, le_adv_min_interval),
> -		HDEV_PARAM_U16(0x000b, le_adv_max_interval),
> -		HDEV_PARAM_U16(0x000c, def_multi_adv_rotation_duration),
> -		HDEV_PARAM_U16(0x000d, le_scan_interval),
> -		HDEV_PARAM_U16(0x000e, le_scan_window),
> -		HDEV_PARAM_U16(0x000f, le_scan_int_suspend),
> -		HDEV_PARAM_U16(0x0010, le_scan_window_suspend),
> -		HDEV_PARAM_U16(0x0011, le_scan_int_discovery),
> -		HDEV_PARAM_U16(0x0012, le_scan_window_discovery),
> -		HDEV_PARAM_U16(0x0013, le_scan_int_adv_monitor),
> -		HDEV_PARAM_U16(0x0014, le_scan_window_adv_monitor),
> -		HDEV_PARAM_U16(0x0015, le_scan_int_connect),
> -		HDEV_PARAM_U16(0x0016, le_scan_window_connect),
> -		HDEV_PARAM_U16(0x0017, le_conn_min_interval),
> -		HDEV_PARAM_U16(0x0018, le_conn_max_interval),
> -		HDEV_PARAM_U16(0x0019, le_conn_latency),
> -		HDEV_PARAM_U16(0x001a, le_supv_timeout),
> -		HDEV_PARAM_U16_JIFFIES_TO_MSECS(0x001b,
> -						def_le_autoconnect_timeout),
> -		HDEV_PARAM_U16(0x001d, advmon_allowlist_duration),
> -		HDEV_PARAM_U16(0x001e, advmon_no_filter_duration),
> +		HDEV_PARAM_U16(def_page_scan_type);
> +		HDEV_PARAM_U16(def_page_scan_int);
> +		HDEV_PARAM_U16(def_page_scan_window);
> +		HDEV_PARAM_U16(def_inq_scan_type);
> +		HDEV_PARAM_U16(def_inq_scan_int);
> +		HDEV_PARAM_U16(def_inq_scan_window);
> +		HDEV_PARAM_U16(def_br_lsto);
> +		HDEV_PARAM_U16(def_page_timeout);
> +		HDEV_PARAM_U16(sniff_min_interval);
> +		HDEV_PARAM_U16(sniff_max_interval);
> +		HDEV_PARAM_U16(le_adv_min_interval);
> +		HDEV_PARAM_U16(le_adv_max_interval);
> +		HDEV_PARAM_U16(def_multi_adv_rotation_duration);
> +		HDEV_PARAM_U16(le_scan_interval);
> +		HDEV_PARAM_U16(le_scan_window);
> +		HDEV_PARAM_U16(le_scan_int_suspend);
> +		HDEV_PARAM_U16(le_scan_window_suspend);
> +		HDEV_PARAM_U16(le_scan_int_discovery);
> +		HDEV_PARAM_U16(le_scan_window_discovery);
> +		HDEV_PARAM_U16(le_scan_int_adv_monitor);
> +		HDEV_PARAM_U16(le_scan_window_adv_monitor);
> +		HDEV_PARAM_U16(le_scan_int_connect);
> +		HDEV_PARAM_U16(le_scan_window_connect);
> +		HDEV_PARAM_U16(le_conn_min_interval);
> +		HDEV_PARAM_U16(le_conn_max_interval);
> +		HDEV_PARAM_U16(le_conn_latency);
> +		HDEV_PARAM_U16(le_supv_timeout);
> +		HDEV_PARAM_U16(def_le_autoconnect_timeout);
> +		HDEV_PARAM_U16(advmon_allowlist_duration);
> +		HDEV_PARAM_U16(advmon_no_filter_duration);
> +	} __packed rp = {
> +		TLV_SET_U16(0x0000, def_page_scan_type),
> +		TLV_SET_U16(0x0001, def_page_scan_int),
> +		TLV_SET_U16(0x0002, def_page_scan_window),
> +		TLV_SET_U16(0x0003, def_inq_scan_type),
> +		TLV_SET_U16(0x0004, def_inq_scan_int),
> +		TLV_SET_U16(0x0005, def_inq_scan_window),
> +		TLV_SET_U16(0x0006, def_br_lsto),
> +		TLV_SET_U16(0x0007, def_page_timeout),
> +		TLV_SET_U16(0x0008, sniff_min_interval),
> +		TLV_SET_U16(0x0009, sniff_max_interval),
> +		TLV_SET_U16(0x000a, le_adv_min_interval),
> +		TLV_SET_U16(0x000b, le_adv_max_interval),
> +		TLV_SET_U16(0x000c, def_multi_adv_rotation_duration),
> +		TLV_SET_U16(0x000d, le_scan_interval),
> +		TLV_SET_U16(0x000e, le_scan_window),
> +		TLV_SET_U16(0x000f, le_scan_int_suspend),
> +		TLV_SET_U16(0x0010, le_scan_window_suspend),
> +		TLV_SET_U16(0x0011, le_scan_int_discovery),
> +		TLV_SET_U16(0x0012, le_scan_window_discovery),
> +		TLV_SET_U16(0x0013, le_scan_int_adv_monitor),
> +		TLV_SET_U16(0x0014, le_scan_window_adv_monitor),
> +		TLV_SET_U16(0x0015, le_scan_int_connect),
> +		TLV_SET_U16(0x0016, le_scan_window_connect),
> +		TLV_SET_U16(0x0017, le_conn_min_interval),
> +		TLV_SET_U16(0x0018, le_conn_max_interval),
> +		TLV_SET_U16(0x0019, le_conn_latency),
> +		TLV_SET_U16(0x001a, le_supv_timeout),
> +		TLV_SET_U16_JIFFIES_TO_MSECS(0x001b,
> +					     def_le_autoconnect_timeout),
> +		TLV_SET_U16(0x001d, advmon_allowlist_duration),
> +		TLV_SET_U16(0x001e, advmon_no_filter_duration),
> 	};
> -	struct mgmt_rp_read_def_system_config *rp = (void *)params;
> 
> 	bt_dev_dbg(hdev, "sock %p", sk);
> 
> -	return mgmt_cmd_complete(sk, hdev->id,
> -				 MGMT_OP_READ_DEF_SYSTEM_CONFIG,
> -				 0, rp, sizeof(params));
> +	ret = mgmt_cmd_complete(sk, hdev->id,
> +				MGMT_OP_READ_DEF_SYSTEM_CONFIG,
> +				0, &rp, sizeof(rp));
> +	return ret;
> }
> 

frankly I would prefer if we do the re-factoring first and only then add new
parameters.

While I am looking at this, I am also really confused about this
JIFFIES_TO_MSEC business. We should actually not store anything in jiffies
or use it in an API. Is there a good reason to keep storing things in
jiffies internally?

Regards

Marcel