linux-kernel - Re: [PATCH v5 13/13] tty: gunyah: Add tty console driver for RM Console Services

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Date:   Tue, 11 Oct 2022 08:02:35 +0200
From:   Jiri Slaby <jirislaby@...nel.org>
To:     Elliot Berman <quic_eberman@...cinc.com>,
        Bjorn Andersson <quic_bjorande@...cinc.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Murali Nalajala <quic_mnalajal@...cinc.com>,
        Trilok Soni <quic_tsoni@...cinc.com>,
        Srivatsa Vaddagiri <quic_svaddagi@...cinc.com>,
        Carl van Schaik <quic_cvanscha@...cinc.com>,
        Prakruthi Deepak Heragu <quic_pheragu@...cinc.com>,
        Andy Gross <agross@...nel.org>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Jassi Brar <jassisinghbrar@...il.com>,
        linux-arm-kernel@...ts.infradead.org,
        Mark Rutland <mark.rutland@....com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Sudeep Holla <sudeep.holla@....com>,
        Marc Zyngier <maz@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Jonathan Corbet <corbet@....net>,
        Will Deacon <will@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Arnd Bergmann <arnd@...db.de>, devicetree@...r.kernel.org,
        linux-doc@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 13/13] tty: gunyah: Add tty console driver for RM
 Console Services

On 11. 10. 22, 2:08, Elliot Berman wrote:
> Gunyah provides a console for each VM using the VM console resource
> manager APIs. This driver allows console data from other
> VMs to be accessed via a TTY device and exports a console device to dump
> Linux's own logs to our console.
...
> +struct rm_cons_drv_data {
> +	struct tty_driver *tty_driver;
> +	struct device *dev;
> +
> +	spinlock_t ports_lock;
> +	struct rm_cons_port *ports[RM_CONS_TTY_ADAPATERS];
> +
> +	struct notifier_block rm_cons_notif;
> +	struct console console;
> +
> +	/* below are for printk console.
> +	 * gh_rm_console_* calls will sleep and console_write can be called from
> +	 * atomic ctx. Two xmit buffers are used. The active buffer is tracked with
> +	 * co_xmit_idx. Writes go into the co_xmit_buf[co_xmit_idx] buffer.
> +	 * A work is scheduled to flush the bytes. The work will swap the active buffer
> +	 * and write out the other buffer.
> +	 */

Ugh, why? This is too ugly and unnecessary. What about passing the kfifo 
to gh_rm_console_write() instead? You do memcpy() there anyway.

> +	char *co_xmit_buf[2];
> +	int co_xmit_idx;
> +	unsigned int co_xmit_count;
> +	spinlock_t co_xmit_lock;
> +	struct work_struct co_flush_work;
> +};
> +
> +static int rm_cons_notif_handler(struct notifier_block *nb, unsigned long cmd, void *data)
> +{
> +	int count, i;
> +	struct rm_cons_port *rm_port = NULL;
> +	struct tty_port *tty_port = NULL;
> +	struct rm_cons_drv_data *cons_data =
> +		container_of(nb, struct rm_cons_drv_data, rm_cons_notif);
> +	const struct gh_rm_notification *notif = data;
> +	struct gh_rm_notif_vm_console_chars const * const msg = notif->buff;

So you did not comment on/address all my notes?

-- 
js