linux-kernel - Re: [PATCH v5 5/7] Bluetooth: Extend btuart driver for join more vendor devices

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Message-Id: <6476BE78-3FE5-465F-8060-2215387323AA@holtmann.org>
Date:   Mon, 16 Jul 2018 14:59:58 +0200
From:   Marcel Holtmann <marcel@...tmann.org>
To:     Sean Wang <sean.wang@...iatek.com>
Cc:     mark.rutland@....com, devicetree@...r.kernel.org,
        Johan Hedberg <johan.hedberg@...il.com>,
        linux-kernel@...r.kernel.org, linux-bluetooth@...r.kernel.org,
        robh+dt@...nel.org, linux-mediatek@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v5 5/7] Bluetooth: Extend btuart driver for join more
 vendor devices

Hi Sean,

>>> Adding an independent btuart.h header allows these essential definitions
>>> can be reused in vendor driver. Also, struct btuart_vnd is extended with
>>> additional callbacks such as .init initializing vendor data, .shtudown,
>>> .recv and .send supporting SoC specific framing for that btuart can
>>> simply adapt to various Bluetooth uart-based devices.
>>> 
>>> Signed-off-by: Sean Wang <sean.wang@...iatek.com>
>>> ---
>>> drivers/bluetooth/btuart.c | 73 ++++++++++++++++++++++++----------------------
>>> drivers/bluetooth/btuart.h | 30 +++++++++++++++++++
>>> 2 files changed, 68 insertions(+), 35 deletions(-)
>>> create mode 100644 drivers/bluetooth/btuart.h
>>> 
>>> diff --git a/drivers/bluetooth/btuart.c b/drivers/bluetooth/btuart.c
>>> index a900aac..65d0086 100644
>>> --- a/drivers/bluetooth/btuart.c
>>> +++ b/drivers/bluetooth/btuart.c
>>> @@ -33,35 +33,11 @@
>>> #include <net/bluetooth/hci_core.h>
>>> 
>>> #include "h4_recv.h"
>>> +#include "btuart.h"
>>> #include "btbcm.h"
>>> 
>>> #define VERSION "1.0"
>>> 
>>> -struct btuart_vnd {
>>> -	const struct h4_recv_pkt *recv_pkts;
>>> -	int recv_pkts_cnt;
>>> -	unsigned int manufacturer;
>>> -	int (*open)(struct hci_dev *hdev);
>>> -	int (*close)(struct hci_dev *hdev);
>>> -	int (*setup)(struct hci_dev *hdev);
>>> -};
>>> -
>>> -struct btuart_dev {
>>> -	struct hci_dev *hdev;
>>> -	struct serdev_device *serdev;
>>> -
>>> -	struct work_struct tx_work;
>>> -	unsigned long tx_state;
>>> -	struct sk_buff_head txq;
>>> -
>>> -	struct sk_buff *rx_skb;
>>> -
>>> -	const struct btuart_vnd *vnd;
>>> -};
>> 
>> I really like to avoid this since it is not clean. Frankly I prefer to keep the btuart.c driver for drivers that really just use H:4 as transport protocol. If the protocol is only H:4 alike and has extra headers, then it should be a separate driver.
>> 
> 
> thanks for letting me know your concern. I think I'm a little over in reusing these existing methods and break something generic and its beauty.
> 
> I'll make the driver be a separate one based on btuart in the next version.
> 
> 
>> The common H:4 handling is abstracted in h4_recv.h already anyway and we can add more pieces if needed. However I also wonder since you have extra framing that the complex H:4 state keeping might be not needed at all. So it could be simplified.
>> 
> 
> okay, I will get rid of h4_recv.h and consider to use more simplified logic to handle the extra framing and its payload.

only if it is already framed by your extra header, but I seem to recall that it will frame it. For example the bfusb.c old driver does frame H:4 as well and then no extra state keeping for H:4 is needed. Just pass the frames up into the core via hci_recv_frame (or hci_recv_diag for vendor diagnostic) and move on with it.

You can of course use h4_recv.h if you need to, but only do that if you are true H:4 stream and have no idea where a frame ends and starts.

Regards

Marcel