linux-kernel - Re: staging: Add MA USB Host driver

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Message-ID: <20200121081306.GG21151@kadam>
Date:   Tue, 21 Jan 2020 11:13:06 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     Vladimir Stankovic <vladimir.stankovic@...playlink.com>
Cc:     "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "devel@...verdev.osuosl.org" <devel@...verdev.osuosl.org>,
        Petar Kovacevic <petar.kovacevic@...playlink.com>,
        Nikola Simic <nikola.simic@...playlink.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Marko Miljkovic <marko.miljkovic@...playlink.com>,
        Stefan Lugonjic <stefan.lugonjic@...playlink.com>
Subject: Re: staging: Add MA USB Host driver

On Mon, Jan 20, 2020 at 09:30:43AM +0000, Vladimir Stankovic wrote:
> +int mausb_enqueue_event_from_user(uint8_t madev_addr, uint32_t all_events)
> +{
> +	unsigned long flags;
> +	uint16_t num_of_completed,
> +		 num_of_events;
> +	struct mausb_device *dev;
> +
> +	spin_lock_irqsave(&mss.lock, flags);
> +	dev = mausb_get_dev_from_addr_unsafe(madev_addr);
> +
> +	if (!dev) {
> +		spin_unlock_irqrestore(&mss.lock, flags);
> +		return 0;
> +	}
> +
> +	spin_lock_irqsave(&dev->num_of_user_events_lock, flags);
> +	num_of_completed = (uint16_t)all_events +
> +			   (uint16_t)dev->num_of_user_events;
> +	num_of_events	 = (all_events >> (8 * sizeof(num_of_events))) +
> +		(dev->num_of_user_events >> (8 * sizeof(num_of_events)));
> +	dev->num_of_user_events  = num_of_completed;
> +	dev->num_of_user_events |= (uint32_t)num_of_events <<
> +		(8 * sizeof(num_of_events));

I might be missing something.  Why can't we just declare two struct
members instead of doing these bit shifts to fit two values into
dev->num_of_user_events?

> +	spin_unlock_irqrestore(&dev->num_of_user_events_lock, flags);
> +	queue_work(dev->workq, &dev->work);
> +	spin_unlock_irqrestore(&mss.lock, flags);
> +
> +	return 0;
> +}

regards,
dan carpenter