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From: Tejun Heo <htejun@gmail.com>
To: "Eric D. Mudama" <edmudama@gmail.com>
Cc: Henrique de Moraes Holschuh <hmh@hmh.eng.br>,
	Soeren Sonnenburg <kernel@nn7.de>, Jeff Garzik <jeff@garzik.org>,
	Linux Kernel <linux-kernel@vger.kernel.org>
Subject: Re: SATA hotplug from the user side ?
Date: Mon, 05 Feb 2007 20:56:01 +0900	[thread overview]
Message-ID: <45C71B51.9000304@gmail.com> (raw)
In-Reply-To: <311601c90701251321s58c8c0e2s9050fbf9c41cabad@mail.gmail.com>

Eric D. Mudama wrote:
> In the ATA spec, the CHECK POWER MODE command (E5h) specifically
> states that it shouldn't alter the power mode of the device.
> Therefore, there should be no harm in checking the power mode of a
> device in STANDBY or IDLE state, and it shouldn't cause the device to
> spin up.  Checking a drive on my bench I confirmed this behavior.

Yes, we can but...

1. As I wrote in the other reply, I don't think that's necessary.
Devices don't spin up on FLUSH_CACHE followed by STANDBY_IMMEDIATE when
they are in Standby state. (Please point out if this isn't true on most
drives)

2. As the code currently stands, we have to rely on SCSI HLD for
shutting down.  We can query power state there and issue shutdown
conditionally and all those will be properly translated by libata but
it's a bit complex.  I'm not sure whether the added complexity is justified.

> With Serial ATA you have to consider the SATA bus PM states as well,
> but that's a different topic of discussion.

I think that can be dealt with separately.

Thanks.

-- 
tejun

  reply	other threads:[~2007-02-05 11:56 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-01-12  7:57 Soeren Sonnenburg
2007-01-12 17:04 ` Jeff Garzik
2007-01-12 22:07   ` Soeren Sonnenburg
2007-01-13  1:55     ` Tejun Heo
2007-01-13  7:22       ` Soeren Sonnenburg
2007-01-15  2:21         ` Tejun Heo
2007-01-22  9:04           ` Soeren Sonnenburg
2007-01-22 21:03             ` Henrique de Moraes Holschuh
2007-01-23  6:23               ` Tejun Heo
2007-01-23 13:10                 ` Henrique de Moraes Holschuh
2007-01-24  2:07                   ` Tejun Heo
2007-01-24  9:09                     ` Soeren Sonnenburg
2007-01-24 15:37                       ` Henrique de Moraes Holschuh
2007-01-25 12:56                         ` Soeren Sonnenburg
2007-01-25 21:56                           ` Henrique de Moraes Holschuh
2007-01-25 21:21                         ` Eric D. Mudama
2007-02-05 11:56                           ` Tejun Heo [this message]
2007-02-05 11:50                         ` Tejun Heo
2007-01-23  6:19             ` Tejun Heo
     [not found] <fa.pn1gmGiSlhDVMiPyzEEm1A66vcY@ifi.uio.no>
     [not found] ` <fa.Od11QHN89ZQ9VkFktF6HvxWuLV0@ifi.uio.no>
     [not found]   ` <fa.vsuV8EVipw4cXaHgzWpaf0q1pAA@ifi.uio.no>
     [not found]     ` <fa.8a1kVu4a2ISeaFZcL3migbjZ5N0@ifi.uio.no>
     [not found]       ` <fa.79JzgEcD2u5B9SYqrw3sr5b+iy8@ifi.uio.no>
     [not found]         ` <fa.DH50RMz6OHKG0AoGA/cChsCW8Ig@ifi.uio.no>
2007-01-25  0:33           ` Robert Hancock

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