linux-kernel - Re: [PATCH v4 2/3] greybus: Add BeaglePlay Linux Driver

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Message-ID: <1bbe7772-09f4-6c5a-8c4d-c88988b34c99@gmail.com>
Date:   Tue, 5 Sep 2023 21:57:52 +0530
From:   Ayush Singh <ayushdevel1325@...il.com>
To:     Krzysztof Kozlowski <krzk@...nel.org>, greybus-dev@...ts.linaro.org
Cc:     devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        gregkh@...uxfoundation.org,
        Vaishnav M A <vaishnav@...gleboard.org>,
        Jason Kridner <jkridner@...gleboard.org>,
        Nishanth Menon <nm@...com>
Subject: Re: [PATCH v4 2/3] greybus: Add BeaglePlay Linux Driver

>> +static void hdlc_handle_rx_frame(struct gb_beagleplay *bg)
>> +{
>> +	u8 address = bg->rx_buffer[0];
>> +	char *buffer = &bg->rx_buffer[2];
>> +	size_t buffer_len = bg->rx_buffer_len - 4;
>> +
>> +	switch (address) {
>> +	case ADDRESS_DBG:
>> +		hdlc_handle_dbg_frame(bg, buffer, buffer_len);
>> +		break;
>> +	case ADDRESS_GREYBUS:
>> +		hdlc_handle_greybus_frame(bg, buffer, buffer_len);
>> +		break;
>> +	default:
>> +		dev_warn(&bg->serdev->dev, "Got Unknown Frame %u", address);
> ratelimit
> Probably as well in several places with possible flooding.

I don't think `hdlc_handle_rx_frame` is the correct place since it only 
processes a single completed HDLC frame.  The more appropriate place 
would be `hdlc_rx` if we want to limit based on the number of HDLC 
frames or `gb_beagleplay_tty_receive` to limit based on the number of bytes.

I would like to ask, though, why is rate limiting required here? Won't 
`serdev_device_ops->receive_buf` already rate limit the number of bytes 
somewhat? Or is it related to blocking in the 
`serdev_device_ops->receive_buf` callback? In the case of latter, it 
would probably make sense to ratelimit based on number of frames, I think.

Ayush Singh